Swindon will go to the polls tomorrow like the rest of the country.

But the town is one of a few places that seems to be a very good guide for how the rest of the country will vote.

You have to go back 40 years to find a general election in the town where the winning MP did not come from the party which went on to form the government.

That was in 1979 when the sitting Labour MP David Stoddart was returned, while Margaret Thatcher’s Conservatives took Number 10.

But why has the town for the last 40 years been so in tune with the national mood of politics?

BBC Wiltshire’s politics reporter Dan O’Brien said: “There are lots of different theories on what the reasons are for this.

"Part of it is Swindon has a higher proportion than most of so-called ‘working families’ – perhaps a reflection of why this is such a popular place to bring up kids.

"Compared to younger and older voters, these families in the middle are a group seen as being far more likely to change their minds at election time and it’s why so many policies are targeted at the ‘typical’ family.

“So that’s one theory. Another is that the town has historically had a reputation as being quite an average place, and as a local resident I don’t mean that in a negative way at all, but in terms of average incomes, price of housing, employment and skills – not much is way above or below what’s typical for the country as a whole so it can be a good barometer.

“But whatever reason there may be for its barometer status, Labour know they need to win back towns like Swindon if they are to get back into Number 10 – and the Tories know they need to hold it. It’s no coincidence Labour’s leader Jeremy Corbyn came here on the very first weekend of the election campaign – and why we’ve since had a raft of Conservative cabinet ministers visit too.”

For the candidates battling to win, the answer is that Swindon, certainly South, reflects the make-up of England in miniature.

Labour candidate Sarah Church said: “The constituency has a bit of everything. It is very diverse in the centre of the town, ethnically and demographically, and there’s something of every other type of community.

“It’s specifically reflective of England, rather than the whole of Great Britain.”

That’s an analysis that the defending Conservative candidate Robert Buckland agrees with. He said: “My postbag as MP contains something of everything, from inner town issues to things like rural crime and there are villages and suburban areas as well. It’s a microcosm of the country as a whole.”

He added: “Things might be slightly changing in North Swindon. We’ve had some large developments in the southern part. But nothing like the expansions in North Swindon, from Abbey Meads and Priory Vale to Tadpole Garden Village. That’s changed the nature of North Swindon a bit.”

The Conservative candidate for North Swindon Justin Tomlinson said: “Over the years we’ve seen the constituency reflect the national mood in many elections, both local and general.”

To show Swindon's 'bellweather' status, one need only look at the historical results. Between the end of the Second World War and 1983 Swindon was a solid Labour town. It had a Conservative MP for just a year, from a by-election in 1969 returned the Tories’ Christopher Ward.

But in the general election in 1970 David Stoddart won the seat and held it for 13 years.

Since 1983, when Swindon, which was still a single constituency, went over to the Conservatives in a landslide win for Mrs Thatcher, it has always been a predictor of the national results.

Conservative MP Simon Coombs continued for 14 years, with two successful defences ion 1987 and 1992, but fell victim to Tony Blair’s New Labour landslide in 1997, where he stood in the newly-created South Swindon constituency.

At that election, two Labour MPs won, Julia Drown in South Swindon, and Michael Wills in the northern half of the borough.

Ms Drown stepped down in 2005, replaced by her party colleague Anne Snelgrove, while North Swindon’s Michael Wills served the whole 13 years of Labour government.

In 2010 two Conservatives were elected, Robert Buckland and Justin Tomlinson; both still in their seat when this election was called.

While we had a hung parliament in 2010 and 2017, Conservatives were the largest single party, and either led a coalition government or formed a minority administration.