IT is known as Little Scotland and on Thursday the thousands of Scots, first and second-generation, who live in the former steel town of Corby, will hold the key to who becomes the seat's new MP.

Such is the Scottishness of this Northamptonshire community that Ed Miliband, in town for his fourth visit and sensing a major political coup, has ordered all 40 Scottish Labour MPs to travel to the Midlands this week to knock on doors and get the vote out for their candidate Andy Sawford .

He knows taking the first Tory-held by-election seat since 1997 with a 1000 majority would be good, but taking it with a 5000 majority would seriously wound David Cameron and continue the political momentum the Labour leader has built up since the Coalition's "omnishambles" Budget.

It was in the economically depressed 1930s that steelworkers from Scotland began heading south, many on foot, to find work and ended up in Corby. By the 1960s, the well-trodden route meant more than half of the town's population was Scottish; today, it is still roughly one in five with around 10,000 Scots voters.

Saltires fly from balconies, there are two Church of Scotland churches, and the town boasts having the biggest Rangers fan club outside Scotland and Northern Ireland.

The Scottish feel of Corby is nowhere more evident than at the Grampian Club, a working men's retreat set up in 1978 to serve the large diaspora from north of the Border. Tartan carpets, clan shields and pictures of Robbie Burns decorate its bars, with a Saltire flapping in the wind outside.

Regular, Charlie Johnston, 73, who came from Glasgow in 1965 to work in the steel factory, is adamant Labour will retake Corby and is dismissive of the town's former Conservative MP, the outspoken chicklit author Louise Mensch, who sparked the by-election after standing down to spend more time with her family in New York.

"She just walked away from the job. In fact, she went into it, knowing she was going to give it up and go abroad. She has cost the country millions because of this by-election. No, the people of Corby have lost faith in the Tories," he said.

Another ex-steel worker David Davies, 59, brought to Corby when he was just two in the 1950s after his father William left Stirling looking for work, is even more dismissive of his now departed MP. "The missing Mensch? We never saw her. They wouldn't even give her an office in the town. Corby will go back to Labour big-time."

Ex-soldier Bob Ritchie, 75, originally from Fife but who has lived in Corby for 35 years, takes a different view. "I'm supporting the Tories. Mensch let herself down, but not the politics. The politics has not changed because she has gone. I hope it stays a Tory seat."

It was in 1979 that the famous Corby steelworks closed, shedding more than 10,000 jobs at a stroke. Unemployment is now 6%, but for those under 25 it is Britain's worst jobless blackspot with a rate of 11%. Yet there are some positive signs; Tesco is building a new store and 85 companies have set up in the second quarter of the year.

Politically, the constituency is mixed. Corby, a working-class town, is staunchly Labour while the more well-to-do rural areas are true blue. Apart from the 1997 Blair landslide when there was a sizeable swing to Labour, the bellwether constituency has always been regarded as marginal; Ms Mensch's majority was just 1951.

Tory candidate businesswoman Christine Emmett brushed aside talk by locals that Ms Mensch's abrupt departure has alienated many people. She said: "We've got over that now. People are looking ahead to elect the next MP not the last one."

Mr Sawford, whose father was a steelworker-turned-MP for Kettering, exudes a confidence that suggests he knows he's within touching distance of a famous victory, but he still warns against complacency. "This is not an easy seat to win. We're fighting for every vote."