Diary: After one fracas, MP has another scandal to fight

It is looking highly improbable that Joyce will ever be a Labour candidate in another election (Rex Features)

There is more trouble for Eric Joyce, the Labour MP and ex-soldier involved in a fracas in a bar in the House of Commons. It was alleged in yesterday's Daily Record that he has been having an affair with a teenager, 32 years his junior. He denies a sexual relationship and is consulting lawyers, but the allegation sorely tested the patience of Labour's leader in Scotland, Johann Lamont, who snapped that – if true – "this makes him unfit to stand for Labour".

It is looking highly improbable that Joyce will ever be a Labour candidate in another election. Even he hinted as much in his only public comment so far on what happened in the Strangers Bar when he tweeted: "I don't actually deserve compassion." But there is nothing the Labour leadership can do to compel him to quit his seat before 2015.

You might think the people of Falkirk hold that power, given that all three parties agreed before the last election that there should be a means by which the voters could sack errant MPs. But that involves changing the law, which is slow.

Nick Clegg published a document in December stating what the Government was minded to do when they got around to legislating. It has been criticised because it proposes that the only MPs vulnerable to the sack would be those convicted of a criminal offence or formally condemned by the House of Commons. At least 57 backbench MPs, from all parties, do not think the grandees of the House of Commons should be given what is effectively a veto over which MPs should be sacked. They have signed a Commons motion that would transfer that power to electors.

But Ed Miliband and his party managers must be secretly relieved nothing has happened. The last time there was a by-election in Falkirk, 12 years ago, Joyce scraped in just 705 votes ahead of the SNP. If Joyce steps down, in the current state of Scottish politics, his seat could fall to the nationalists.

Cameron rides into tale of Brooks' police horse

Amid the many disturbing stories coming out of the Leveson Inquiry, at least one has added to the jollity of the nation – the story of the retired police horse loaned to former News International chief executive, Rebekah Brooks.

Raisa the horse, or someone purporting to be the horse, is tweeting to almost 2,000 followers, while Westminster laughs itself hoarse over the terrible puns generated with each flick of this extraordinary tale. But David Cameron is not laughing, because of the remark made months ago by a former News of the World reporter, Paul McMullan, who claimed the Prime Minister "regularly" went riding with Brooks. "I know, because as well as door-stepping celebrities, I've also door-stepped my ex-boss by hiding in the bushes, waiting for her to come past with Cameron on a horse," McMullan said.

Yesterday, the PM was asked on Channel 5 News whether he had ever gone hacking on Raisa. "I have been riding with Rebekah Brooks' husband, Charlie Brooks," he said. "He is a friend of mine for 30 years standing and a neighbour in my constituency so that's a matter of record, but since I have been Prime Minister I think I have been on a horse once and it wasn't that one."

Marsha bows out (or is that curtsies?)

One Labour seat where there definitely will be a by-election is Bradford West, where the sitting MP Marsha Singh has resigned after 15 years, because he says that ill health prevents him doing the job properly. When he was elected in 1997, one of the first items of internal post Marsha received was an invitation to a meeting for women Labour MPs. He politely explained that Marsha, in his case, was not a woman's name. The by-election will be on 29 March.