At the age of 70, and after 40 years of service, who can blame Sir Alan Beith for this week announcing his intention to step down at the next general election? The Berwick-upon-Tweed MP is the longest serving Liberal since David Lloyd George, so it’s unsurprising that he’s ready to say goodbye to Westminster.

With Sir Alan out of the equation, the Conservative campaigns team will be marking Berwick high on their target list (Labour enjoyed a mere 13.2% share of the vote in 2010, and have never won there). Anne-Marie Trevelyan, who contested the seat last time round, already has an active online campaign set up for 2015. Given that, as Conservative Home noted, she reduced the Lib Dem majority from 23.9% to 7% last time round, she’s surely got to be viewed as a serious contender. “This constituency is my home and I don’t want to be the MP for anywhere else,” she writes on her Team Trevelyan website. Whoever is selected to fight for the Lib Dems will have a battle on their hands.

But the party will be hoping for gains elsewhere, not least in Bristol South, where veteran Labour MP Dawn Primarolo is on her way out as well after a quarter of a century. Karin Smith, who was selected to run in her place on an all-women shortlist, is described by Primarolo as “a relentless campaigner”. But while the constituency is considered one of the safer of Labour’s seats, it’s worth noting that in 2010 Labour suffered a 7.55% swing to the Lib Dems.

Perhaps the most interesting contest, at this stage anyway, looks set to be fought in Hampstead and Kilburn, where the indomitable actress turned parliamentarian Glenda Jackson is retiring. It was a wisp of a Labour win last time round – just 42 votes separating Jackson from her Conservative rival, and fewer than 900 between her and the Lib Dem candidate – and the race is already on. Camden councillor Simon Marcus, who succeeded in pushing BNP’s Nick Griffin into third place in Barking in 2010 – was selected earlier this year for the Conservatives. The founder of a boxing academy for excluded teenagers, one imagines the gloves will come off against the Lib Dem hopeful – former radical turned counter-extremism campaigner Maajid Nawaz.  And hoping to retain Hampstead’s reputation for embracing champagne socialism will be Tulip Siddiq, another Camden councillor with politics in the family (her grandfather founded Bangladesh and she is the niece of its current prime minister).

A handful of other MPs have already announced plans to stand down, including Labour’s John Denham, who won in Southampton Itchen with just 192 votes last time, making it a key Tory target, and Mid Dorset and North Poole MP Annette Brooke, whose majority of just 269 for the Lib Dems means the Conservatives will be eyeing it hungrily (last time round saw a swing in their favour of 6.27%). And then there’s the departure of Eric Joyce from Falkirk, whose exit has ignited what may be a defining battle for the future of the Labour Party over just where the unions stand. Just 21 months until the election!