The Welsh heart was willing, the dragon-flag-waving crowds were willing Geraint Thomas on up the steep final ascent of Belmont, eight kilometres from the finish here, but four weeks of partying since the local hero won the Tour de France had taken their toll. Thomas was perfectly set up by his teammates and put in a searing attack, but when the Frenchman Julian Alaphilippe came flying past, Thomas looked like a man who realised suddenly and painfully that he had bitten off more than he could chew.

“I had to give it a go, being on home roads and so close to where I grew up. I knew the climb but once I went I was thinking: ‘What have I done?’” Thomas said.

“When Alaphilippe went over the top I thought there was no way I could go with that, so I got back in the wheels. It was nice to have a dig but I don’t have the legs to finish it off.”

Team Sky’s collective effort was enough to briefly sow chaos in a peloton that had looked to be heading inexorably for a bunch finish, but the riders they impelled off the front were from Quickstep Floors, hot favourites for this race along with Thomas’s squad. Alaphilippe and Bob Jungels escaped with the Frenchman Jonathan Hivert and the Dane Mads Würtz Schmidt and Thomas was forced back into a team role to ensure that Sky’s nominal leader, Wout Poels, did not lose ground.

After the finish, Thomas was whisked away for yet another round of glad-handing, this time to celebrate the renaming of the national velodrome – which stands out from the centre towards the Llanwern steel works – in his honour. “It’s strange,” he said. “You dream of winning bike races and getting across the line first, not the aftermath and everything that goes with it, having velodromes named after you, going pitch side at the Emirates, Arsenal jerseys with Thomas on the back. It’s really nice.”

Jungels sped clear of Alaphilippe and company but was retrieved in the final kilometre where the second part of the Quickstep pincer movement came into play: the sprinter Fernando Gaviria gained a couple of lengths lead in the last 200m, only to be overhauled by the Australian Caleb Ewan and the German André Greipel, with the latter veering right to take his sixth Tour of Britain stage win and with it the leader’s jersey.

Students of sprint politics could savour the moment. Greipel, a loyal servant to Lotto-Soudal since 2012, had been abruptly dumped over the summer as they opted for a newer, shinier sprinter in Ewan. Afterwards, he made tactful noises about his happy history with the Belgians, but he must have been laughing inwardly.

Thomas had led the field out of the start among the sand dunes and pines of the Pembrey Country Park on the coast south of Carmarthen – and around part of a new custom built racing circuit for future Thomaslets – en route for 108 miles that turned into a second triumphant homecoming after his official return to Cardiff following his Tour de France win in July.

Tiny villages such as Kidwelly and sedate market towns such as Llandovery were a sea of Welsh dragon flags and it was all of three miles into the race before the first fan in full Welsh national dress, stovepipe hat and all, could be spotted on the roadside. Life-size leeks and daffodils were in evidence as well, along with tots in jerseys celebrating Wales’s other hero of the summer, Gareth Bale.

On Monday, the race takes on a different tenor, with a raft of hills in the heart of Devon – one sprint is at the appropriately named village of Nomansland – before a brutal loop out and home from the finish town of Barnstaple, up on to Exmoor through Bratton Fleming for a rollercoaster ride along the north Devon coast. The combine harvesters may be largely back in their barns now with the wheat fields empty, but the chaff should be sorted out well before the final sprint alongside the river Taw.