Marin Cilic says it was difficult to adjust to conditions at the Rod Laver Arena after Australian Open organisers closed the roof for the men’s final.

Roger Federer beat Cilic 6-2 6-7 (5-7) 6-3 3-6 6-1 to win a sixth Australian Open and 20th Grand Slam title.

Temperatures of 37C would not normally invoke the extreme heat policy (40C), but organisers said the humidity was behind the decision to close the roof.

“Mentally it was tough,” said losing finalist Cilic about the roof closure.

“Throughout the tournament I played all my matches outdoors, also preparing for a hot day, 38 degrees. Then first match for the final to play with the roof closed, it’s difficult.

“I have to say that decision, could it have been different? I guess so.

“It was just a little bit difficult to adjust, especially the beginning of the match. With the roof closed, it was way, way cooler than I expected.

“That was very, very difficult, especially for the final to be in that kind of a situation.”

‘Federer one of best ever indoors’

Former Wimbledon champion Pat Cash said the indoor conditions favoured Federer.

“It’s an outdoor tournament. Why is the roof closed?” Cash told BBC Radio 5 live.

“The way Roger plays, he swings so hard at the ball and takes it so early, any wind or variation of the ball moving will take it away from him.

“It’s why he’s one of the best players ever indoors.”

Federer said he was “surprised” by the ruling, but that playing indoors did not affect his preparation.

“I was surprised to hear they had the heat rule in place for a night match,” said the 36-year-old Swiss. “I never heard that before.

“When I arrived to the courts, I was totally ready to play outdoors. They told me they were thinking it will probably be indoor. Then they kept me posted along the way.

“Half an hour before, we got the word that it’s going to be indoors. For me, it doesn’t change anything in the preparation, to be honest. I was ready for either.”

‘I can’t believe they’ve closed the roof’

During the first week of the Grand Slam, players battled through two days of 40C heat fully exposed to the conditions, as organisers declined to invoke the heat policy.

However, the Australian Open said the referee’s decision on Sunday was based on “qualified and professional advice from the Bureau of Meteorology and the tournament’s chief medical officer” at Melbourne Park.

The humidity at the start of the match, measured using the Wet Bulb Globe Temperature, was 32.6 – exceeding the threshold of 32.5.

“At no other time during the event this year has the WGBT reading reached the threshold,” organisers said in a statement.

But it was a decision that was still met with disdain from those watching the final.

“I can’t believe they’ve closed the roof,” said British doubles player Jamie Murray on Twitter.

Former British number one Greg Rusedski added: “Absolutely ridiculous that the roof is closed for the Australian Open. Grand Slams are outdoor events. Yes it’s hot but the court is under shade and an evening match.”

Analysis – ‘hard to argue in extreme conditions’

BBC tennis correspondent Russell Fuller

It was an extremely marginal call by the referee to close the roof, but the decision will have been taken in the knowledge that Simona Halep was treated in hospital for dehydration after the women’s final.

According to the Australian Bureau of Meteorology, the humidity in Melbourne was significantly lower for the start of the men’s final than it had been 24 hours earlier. But it was five degrees hotter – a stifling 37 degrees – when Federer and Cilic got underway.

The index was hovering right on the threshold to trigger the extreme heat policy when the players began their warm up, and therefore the referee was able to exercise his discretion to close the roof.

It was a surprise when the news filtered through ahead of this night time final. It was an advantage for Federer, given his prowess indoors, and he has also benefitted from being able to play six of his seven matches at night in each of the last two years.

But as someone who takes the view that the roof on the three main courts should be closed more readily (and play halted on the outside courts) on these extreme Melbourne days, then it is hard to argue against it when the threshold is finally breached.

Roger Federer said “age is not an issue” after he beat Marin Cilic to win his sixth Australian Open and 20th Grand Slam title at the age of 36.

The Swiss second seed won 6-2 6-7 (5-7) 6-3 3-6 6-1 to retain the title he won 12 months ago.

Ken Rosewall, who won the 1972 Australian Open at 37, is the only man older than Federer to have won a major singles title in the Open era.

“I’ve won three slams now in 12 months. I can’t believe it myself,” he said.

“I’ve just got to keep a good schedule, stay hungry, then maybe good things can happen. Then I don’t think age is an issue, per se. It’s just a number.

“But I need to be very careful in my planning, really decide beforehand what are my goals, what are my priorities. I think that’s what’s going to dictate how successful I will be.

“Exciting times ahead. As a professional, it’s what we do. But I’m happy I’m in that position right now.”

• How Federer won the Australian Open
• Federer claims sixth Melbourne trophy
• Wozniacki wins first Grand Slam title

Federer was playing his 72nd Grand Slam tournament, and making his 19th appearance in the main draw in Melbourne.

After a gap of almost five years between winning his 17th and 18th major titles, he has now won three of the last five, having also claimed an eighth Wimbledon title in July.

Remarkably, Federer has now won 10% of the 200 men’s singles titles on offer at the majors since tennis turned professional in 1968.

Asked how he continues to thrive at the top of such a competitive sport, Federer paid tribute to his wife and parents, adding: “I think by not overplaying, not playing every tournament possible.

“I enjoy practice. Not minding the travel. Having a great team around me, they make it possible.”

Federer was tearful as he accepted the trophy, saying: “It was what it was. I wish it wasn’t so sometimes.

“At the same time, I’m happy I can show emotions and share it with the people.

“If I got emotional, it’s because it was a full crowd again. No people in the stadium wouldn’t make me emotional, I’ll tell you that. This is for them really also.”

Cilic rues missed chance in decider

Cilic made a poor start, losing his first two service games and quickly falling 4-0 behind, and he felt the decision to close the roof under the extreme heat rule played a part.

“I didn’t mind to have the roof closed, but it was a huge difference in temperature from having outside 38C,” said the Croatian sixth seed.

“Then when you came in, it was like 23C or 24C, I don’t know. It was way cooler than I expected.”

Both men have strong records indoors but Federer was unsure whether the decision to use the roof would benefit him.

“I didn’t mind the heat, to be honest,” said the Swiss.

“I thought maybe for a bigger guy like Marin, maybe it’s also going to slow him down faster throughout the match. At the end, it’s not my decision. They kept me posted along the way.”

It was the ninth time in 10 meetings that Cilic had lost to Federer, but he felt he missed a great chance when he was pushing for the break at the start of the final set.

“I was hitting the ball great. I was just playing phenomenal,” he said.

“Then first game of the fifth set was more or less crucial at the end with having those break points that I didn’t convert.”

Reaction – ‘Astonishing then, incredible now’

‘It looks like he can go on forever’

Former British number one Andrew Castle: “It’s the 127 other people in the draw who should be crying. Imagine what the outpouring is going to be when he announces he doesn’t want to play any more – when he’s concluded this amazing career.

“Some people will be surprised about the emotion that he’s showing on his 20th but that’s the depths that you have to go to to win these things. That’s the amazing thing along with his tennis, he keeps wanting to do this. It’s a charming moment and you can see what it means.”

Former Australian Open finalist John Lloyd: “What I loved about it is that he’s surprising himself. He can’t almost believe it. We all look at him and take it for granted but he doesn’t take it for granted. It’s a challenge all the time.

“Every time you see him you wonder if it’s going to be the last time, but he looks like he can go on forever.”

Roger Federer won his sixth Australian Open and 20th Grand Slam title with a five-set victory over Marin Cilic.

The Swiss lost five games in a row as he dropped the fourth set but recovered to win 6-2 6-7 (5-7) 6-3 3-6 6-1.

Federer, 36, becomes only the fourth player after Margaret Court, Serena Williams and Steffi Graf to win 20 or more major singles titles.

“It’s a dream come true and the fairytale continues,” said Federer, who has won three of the last five majors.

• Reaction to Federer’s Australian Open win

The final was played under the Rod Laver Arena roof as the tournament’s extreme heat policy was invoked.

Despite starting at 19:30 local time in Melbourne, the conditions were if anything more testing than 24 hours earlier, when Caroline Wozniacki and Simona Halep played to the point of exhaustion in the women’s final.

With the roof closed and air-conditioning taking the edge off the temperature, Federer and Cilic played out a gripping contest over three hours and two minutes.

After a poor start, Cilic looked to have the momentum when he won five games in a row to force a fifth set, but Federer clung on to his serve at the start of the decider and got the key break in the following game.

The Swiss ties the record for men’s Australian Open titles at six with Novak Djokovic and Roy Emerson, and moves four clear of Rafael Nadal in the all-time list for male Grand Slam champions on 20.

“I’m so happy, it’s unbelievable,” Federer added. “After the year I had last year, it’s incredible.”

Federer holds off Cilic fightback

Cilic, 29, had come into the final brimming with positivity after an impressive run to the final that included a quarter-final win over Nadal, but he made a desperate start.

He won just four points in losing the opening four games, and Federer fired down back-to-back aces on his way to serving out the set after 25 minutes.

The Swiss saw off two break points early in the second, roaring “come on!” as he pulled a forehand winner down the line, and then resumed his assault on the Cilic serve.

Three break points were saved, the third with a second-serve ace, as Cilic edged his way into a tie-break and a chance to claw his way back into the match.

The 2014 US Open champion did just that after a huge cross-court forehand brought up two set points, and he smashed away the second to level.

Federer appeared to have regained control when a deep return drew an error as he broke for 4-2 in the third, and a fabulous half-volley pick-up said the confidence was flowing as he moved ahead again.

With a point for a double-break early in the fourth, Federer appeared as good as home, but his first-serve began to falter and Cilic ripped into the second serve with his huge forehand.

After two hours and 10 minutes he finally broke the Federer serve, and a jolt of adrenaline coursed through the Croat – and the crowd – as this unexpected fightback took him to two sets all.

Federer was now struggling to contain the world number six, and was relieved to see a return hit the net on break point at the start of the fifth, before roaring as a serve saw off a second chance for the Croat.

The Swiss had halted the momentum and in the next game he grabbed it for himself with a deep, fizzing return that Cilic could not handle.

Nerves were still apparent as the eight-time Wimbledon champion urged himself on during the changeover, but he was not about to let his opponent back in, and another break of serve all but made sure.

There was time for one more moment of uncertainty for Federer when, just as in last year’s final, he was forced to wait on match point for Hawk-Eye to confirm that he had indeed retained the title.

Roof closed in testing conditions

The decision before the match to keep the roof closed was greeted with surprise by those in Rod Laver Arena.

As forecast, the temperature in Melbourne during Sunday reached a very testing 37.5C, but that was below the 41C experienced earlier in the tournament, when the extreme heat rule was not involved.

However, the rule is not purely based on ambient temperature, but also other factors such as humidity, wind speed and angle of sun, known as the Wet Bulb Globe Temperature (WBGT).

“The tournament referee made this decision based on qualified and professional advice from the Bureau of Meteorology who are on site, and the tournament’s chief medical officer,” read a Tennis Australia statement.

“At no other time during the event this year has the WBGT reading reached the threshold.”

What the BBC commentators said

Former Wimbledon champion Pat Cash on Radio 5 live: “It was a good performance from both players. You’ve got to hand it to Cilic, he had to play his best tennis and keep it up. That was the problem.

“Federer was consistent the whole way through. Other than a few double faults and a few patches, it was good consistency.”

BBC tennis correspondent Russell Fuller: “Federer has previously won 19 of these, but he has a look of a man who’s never done it before. He may be 36, but he shows no sign of ageing. He’s proved yet again he’s too good for the rest of the world.”

Match stats

Federer’s route to the title