Boggy ground on the site marked for a $47 million replacement Kopu bridge upstream of the existing one-lane gateway to the Coromandel Peninsula left Prime Minister John Key turning a ceremonial first sod on the seaward side instead yesterday.

Mr Key, who recalled once being delayed for a National Party meeting for an hour and a half while queuing to cross the elderly structure, broke the ground on private land to be screened by landscaping once the new bridge is ready by Easter 2012.

Lending extra grunt to his spade was 94-year-old retired farmer George Williams, who was first across the 465m bridge with his brother and cousin on opening day in 1928, after the lads made a break on their bicycles from an official parade.

Asked who was first, he said: "I think it was a dead heat."

But as sole survivor, he hopes to take line honours again when the new two-lane bridge is completed, even if that means swapping the two-wheel dash of his youth for a mobility scooter.

Mr Williams, now of Matamata, said the bridge made a huge difference to a district which previously relied on ferries and barges to cross the mighty Waihou River. He was able to drive cattle across the bridge before traffic lights were installed in the 1960s, after which vehicle queues grew and lobbying began for a replacement.

Mr Key could not believe "how much of a headache and how much dissatisfaction has come from one very small bridge" and challenged lead contractor HEB Construction, of Pukekohe, to see if it could finish the job by the 2011 summer.

Transport Minister Steven Joyce said construction had been brought forward two years with funds from the Government's $500 million "jobs for growth" plan, and Thames-Coromandel Mayor Philippa Barriball looked forward to connecting more New Zealanders "to our beautiful region".

Mr Joyce apologised for arriving late, blaming a car which stopped in front of him on the Auckland end of the bridge for an occupant to take a photograph of its traffic lights turning red.

Transport Agency regional highways manager Kay Clark said that although she expected the project would be completed as soon as possible, considerable forced ground settlement was needed before the bridge and its 2.5km of approach roads could be built.