In my July prediction of the general election result, I put Hendon at the top of the list of seats I forecast Labour to gain from the Conservatives.

It’s not the seat with the smallest Tory majority in the country; nor is it number one on Labour’s target list (in both cases that’s Warwickshire North).

But nonetheless I’m saying it’s the seat it will be easiest for Labour to gain next year.

Here’s why.

1. This was the result at the last election:

Matthew Offord, the Tory candidate, took the seat from Labour’s Andrew Dismore on a 4.1% swing. But this left Offord with a majority of only 106. A swing to Labour of just 0.1% would see him lose. That’s roughly the equivalent of voters in just two of Hendon’s residential streets switching from Tory to Labour.

2. Labour’s Andrew Dismore is standing again. He’s been able to maintain a profile in this area of north London thanks to his election in 2012 as the London assembly member for Barnet and Camden. He’s also been planning for this rematch for some time. There is no love lost between him and Offord. At the declaration in 2010, Dismore said: “This has not been a clean fight. In my view it’s been a pretty dire campaign. It’s my eighth public election and I have never seen such a barrage of personal slurs and lies in this campaign.”

3. Dismore became MP for Hendon in 1997. Long-time residents of the constituency are bound to remember him from his 13-year stint as their member of parliament – though their memories could just as well be positive as negative. Offord, meanwhile, will have served only one term.

4. As suggested by May’s local elections, any national swing from Conservative to Labour will be bigger in London than elsewhere in the country. This is why I didn’t put the even more-marginal Warwickshire North or Thurrock on my list of Labour gains.

5. In an opinion poll commissioned by Lord Ashcroft in May 2014, Labour had an eight-point lead over the Tories in Hendon. This represented a 4% swing – 40 times greater than the one necessary to take the seat. Look out for more polls in seats like Hendon between now and polling day, including more from Lord Ashcroft.

6. One final point that may or may not prove significant. Matthew Offord’s opposition to same-sex marriage led to a spat on the floor of the House of Commons with Mike Freer, Tory MP for neighbouring Finchley and Golders Green. Whether this helps or hinders him in his quest for re-election remains to be seen, but I can’t imagine the incident made for smooth relations within theirrespective local Conservative associations.

If Labour doesn’t win Hendon at the election I will be absolutely gobsmacked. It would also mean Ed Miliband was heading for a heavy defeat and the country could be set for a Conservative majority government.