Christopher Slamon’s body was found by police divers on June 3, after he had gone missing while swimming with friends two days before.

At St Pancras Coroner's Court, the inquest heard that Chris had undiagnosed coronary heart disease and high blood pressure. Pathologist Dr Liina Palm said this had caused his heart attack while swimming in the pond on June 1.

She told the court that Chris's arteries from the right-side of his heart had narrowed by 90 per cent and 75pc from his left. Dr Palm added that while there wasn't any water in Chris's lungs or stomach, it was possible that he had "dry" drowned. Under questioning from his wife, Jessica, she said that if he had the heart attack on land, he may only have survived if CPR had started immediately.

On the morning of his death, the architect received a text from a friend James Dawson, asking if he wanted to go swimming. They met shortly after 8am and Chris proceeded to swim an anti-clockwise lap around the pond on Hampstead Heath, which usually took ten minutes.

Assistant coroner Jonathan Stevens heard that Mr Dawson had got out of the pond at around 8.15am. They had known each other for 30 years.

He said: "I was in a rush to take my son to football, so I got out of the pond. I looked back and I couldn't see him. That's not unusual, that's happened quite a few times before, you don't expect to see them.

"After I got changed, I left to get into my friend's car, and looked back but couldn't see him. I didn't think anything of it."

It was only when Mr Dawson tried to call Chris hours later to arrange meeting up for the FA Cup final that day that the alarm was raised. After attempts to reach the 54-year-old by text and phone, he rang Jessica. She said she thought he was with them. They then went down to the pond and found his clothes in the changing rooms and told lifeguards.

The two lifeguards on duty Marius Bukis and Martin Ackentill gave evidence at the hearing. Mr Ackentill said that there had been no sign of anybody getting into difficulty and as lifeguards they were trained to spot problems before people got into difficulty.

He said: "You pick up on little things, you watch what happens really closely. Often [a lifeguard] will get on the board but will be 50-60 metres away, just watching what is going on if you think someone is getting into trouble. You'll follow that person around."

They both said they hadn't spotted anybody struggling in the water. Jessica asked them whether there is need for another lifeguard on the other side of the pond to watch people.

In response Mr Bukis said that there is somebody on the other side of the pond on busier days.

Summing up, Mr Stevens gave a determination of accidental death. He said that Chris had died of drowning, with a heart attack, coronary heart disease and high blood pressure as contributing factors.

He said: "It seems that Chris suffered a heart attack which happened in that time from 8am to 8.30am."

Chris' family declined to comment after the hearing. However after his death in June Jessica said: "My husband was a wonderful father to our two lovely girls. "He accidentally drowned swimming in the pond he loved and swam in regularly. The support from his many friends and family has been overwhelming and a true reflection of the huge personality he was.

"We would like to thank all the various authorities involved, in particular the police and the lifeguards at Highgate Men's Pond."