He started the job 45 years ago. Now he is getting to finish it.

Neil McDougall, 65, was one of the construction workers who built the first stretch of the M74 back in 1963. The Hamilton by-pass was one of Scotland's first stretches of motorway and its main route to England. Yesterday Mr McDougall started building the road's final, missing, link.

"It's a real pleasure to be working here - finally," Mr McDougall said yesterday, after giving up the seat in his digger to First Minister Alex Salmond, who cut the first sod for the motorway in torrential rain.

The road that began with the Hamilton by-pass in 1963 became the M74. Mr McDougall and Mr Salmond were carrying out a ceremony for its last five miles, the much-mooted M74 completion or M74C from Carmyle to the southern end of Glasgow's Kingston Bridge.

The bill for the five miles will come to around £650m, £2000 an inch, and the most expensive tarmac ever laid in Scotland. It will also, according to some estimates, deliver 20,000 jobs, a post for every yard of asphalt.

Mr Salmond yesterday said: "Regeneration will be a direct result of the completion of the M74, helping to tackle pockets of unemployment through development of prime sites along the Clyde Corridor and areas in Glasgow's east end and south side such as Rutherglen and Cambuslang."

He was flanked by Steven Purcell, the Labour head of Glasgow Council and one of a succession of city leaders to champion the motorway.

Mr Salmond and Mr Purcell had worked together to secure the Commonwealth Games for Glasgow but most regeneration experts agree the M74 by far outweighs the Games in importance.

Richard Cairns, chief executive of Glasgow Chamber of Commerce, said: "We have been waiting over 40 years for this missing link in the city's ring road to be completed. Not only will this new section reduce congestion through the city centre, but it will greatly reduce journey times from the area to key markets, stimulating the economy and creating jobs.

"The completion of this key piece of transport infrastructure in the west of Scotland is to be welcomed by business and the community generally."

The Green lobby had fought to stop the new motorway, claiming it would hamstring government efforts to cut greenhouse gases. Patrick Harvie, the Glasgow Green MSP, questioned the deal struck by the government and the consortium building the road, Interlink M74. The consortium had been the only official bidder for the work.