THE UK leader of the Liberal Democrats has downplayed his party’s chance of pulling off a shock win in the Richmond Park by-election today.

On a flying visit to Holyrood and the LibDem-held Holyrood seat of Edinburgh West, Tim Farron said former Tory MP Zac Goldsmith remained the favourite in the knife-edge race.

He told The Herald the mood in the seat was very positive and support was moving to the LibDems “at a reasonable speed”, but added: “You’ve got to say Zac’s still the favourite.

“We start 23,000 votes behind. It’s a heck of an ask in four and a half weeks.

“Zac Goldsmith, whatever one thinks about him, has a very strong personal recognition.

“No sitting MP who resigned and caused a by-election then stood has lost for 30 years.

“It’s a tough thing to try and take a seat in a by-election off an incumbent, and a rare thing.”

Mr Goldsmith resigned last month after the government backed a third runway at nearby Heathrow airport.

He is now standing as an Independent, but with the tacit support of the Conservatives and Ukip, who are not standing.

The Greens have stepped back to help LibDem challenger Sarah Olney, but Labour are fielding a candidate.

The LibDems want to make the contest about the government's handling of Brexit, capitalising on Mr Goldsmith backing Leave while the constituency was overwhelmingly for Remain.

Asked if Labour would be to blame if the LibDems lost today, Mr Farron said: “Possibly.”

Sir Bob Geldof yesterday backed Ms Olney’s campaign, accusing Mr Goldsmith of being a “poster boy for the Brexiteers”.

He said: “The plain fact is that Zac is a political failure. He’s not only failed but betrayed the people of Richmond, who like the rest of London, voted overwhelmingly to stay in Europe.”

Mr Farron also said the SNP’s plan for a bespoke Brexit deal in which Scotland could stay in the EU single market while the rest of the UK left was a “non-starter” and a “distraction” from the more credible LibDem plan for a second referendum on the terms of Brexit deal.

He said: “The real issue is can Nicola Sturgeon put aside this obsession about separation just for long enough for us to get something that’s good for Scotland and the whole of the UK? Much as I understand what Nicola Sturgeon is trying to do, for the good of every part of the UK, she ought to get behind our much more plausible route.”