The fourth edition of the one-day race, a variation of the Olympic road race route used for London 2012, starting on Horse Guards Road in St James’s Park and streaming west through the capital, saw a six-man move get away in the early stages.

Spain’s Jonathan Lastra, Luxembourg’s Jempy Drucker and the Belgian pair of Jens Wallays and Jonas Rickaert were joined in the breakaway by Britain’s Matt Holmes and Dexter Gardias.

Their progress was halted by a neutralisation in the race, after two serious crashes in the sportive event, which took place ahead of the men’s elite event.

The first incident reportedly saw a man come off his bike and hit a tree, requiring an air ambulance, while the second rider was treated for head injuries in a separate incident.

After a break of nearly 20 minutes, racing resumed and saw Team Sky, including Tour de France winner Chris Froome in their line-up, launch an offensive to close the gap to the breakaway.

Thomas opted to go clear of the peloton with 50 kilometres left of the 200km course, the Briton making contact with the break, before moving away on his own.

Thomas, who will compete alongside Froome in the men’s Olympic road race, held off the peloton until the final five kilometres.

It left the race destined for a sprint finish, with 35-year-old Boonen proving to have the strongest kick to win in a time of 4 hours 43min 55sec.

“It was a very, very hard day today,” Boonen told BBC Sport.

“At a certain point I was dropped two times.

“I came back at the team did an incredible job chasing everybody down.

“When we came to the last corner I was waiting for the perfect moment, I then saw the 200 metres sign and I thought I’d try it and see what happens.”

The Belgian, who rides for Etixx - Quick-Step, ended on the same time as Australia’s Mark Renshaw and Michael Matthews, second and third respectively.