It is your first marathon, record temperatures have turned London into an oven and you are on a broken down train six miles from the starting line.That was the dilemma facing Gary Davison, 39, and Peter Cappuccio, 42, both of Mattishall, near Dereham, on Sunday when bad luck turned the gruelling 26 mile race turned into a crippling 32 mile slog.

It is your first marathon, record temperatures have turned London into an oven and you are on a broken down train six miles from the starting line.

That was the dilemma facing Gary Davison, 39, and Peter Cappuccio, 42, both of Mattishall, near Dereham, on Sunday when bad luck turned the gruelling 26 mile race turned into a crippling 32 mile slog.

The pair was among hundreds of competitors facing an unwelcome six mile warm up when a train broke down blocking the Docklands Light Railway line from east London to the race at Blackheath.

Not knowing which way to go they joined a mass of runners on a dash across the capital to reach the starting line before the entrants moved off.

The pair recalled a blur of landmarks such as Canary Wharf and at one point found themselves marching the wrong way down the marathon route they would be running along hours later.

They arrived at the starting line with minutes to spare and only just enough time to find their numbers and check in their bags before setting off on the marathon proper.

Mr Davison, who is a crew manager in the fire service based at Norwich, said: “The train was jam packed with competitors and it took a little while for everyone to realise what had happened.

“When we realised we were going to have to find our own way we started to panic because we were not 100pc sure where we were going, we just had to follow this mass of runners and hope they knew the way.

“We ended up walking part of the way back down the route we would be running and arrived at the start literally a minute beforehand.

“All we had time to do was worry as we tried to find out where our bags went, to change our shoes and get our numbers.”

Father-of-two Mr Cappuccio said the pair had stayed overnight at a hotel close to the ExCeL conference and exhibition centre in east London and had thought they had left plenty of time when they set off at 8am.

“We got there about three minutes before the start. It was a case of checking our bags on the lorry and away we go,” he said.

Despite the setback - plus the 22C heat that tested the endurance of most of the 36,000 runners - Mr Cappuccio rose to the challenge, turning in a time of four hours two minutes.

He said: “I enjoyed the run. With the atmosphere and the crowd and everything, it was a brilliant event. A fantastic occasion. But the heat was so intense - that was the telling factor for me.”

He hopes to have raised about £2,500 for Cancer Research UK.

Mr Davison said he kept going well for the first three-quarters of the race but was suddenly struck down by a crippling pain in his hips that reduced him to walking for most of the last six miles.

He almost stopped but said he was spurred on by a call to his family and the sight of a man dressed as a fire engine overtaking him and finished the race in five hours 32 minutes.

The sweltering temperatures meant his fire service training came in useful as he used techniques to reduce body temperature such as pouring cold water on his wrists to cool his blood.

Mr Davison had been training hard, running about 18 miles three times a week and had been hoping for a time of about four hours twenty minutes.

“I don't know whether what happened affected my performance but it was pretty frustrating after my preparation,” he said.

He raised £3,000 for The Prostrate Cancer Charity in honour of his father Jim, who died of the disease three years ago.

A spokesman for Serco Docklands, which runs the DLR service, confirmed that a train broke down at Mudchute at 8.29am on Sunday, disrupting services between Crossharbour and Greenwich until 1.58pm that day.

He said that a shuttle bus service had been laid on between Greenwich and Lewisham and Greenwich foot tunnel had been opened to pedestrians.

Tony Thomas, managing director of Serco Docklands apologised to marathon competitors and spectators affected and said it was investigating what had happened.

To sponsor Peter call 07969 488390 or Gary call 01362 850165.