The Lib Dems, buoyed as they are by their success in this month's Witney by-election, will give this by-election everything they've got. "We threw the kitchen sink at Witney," one senior Lib Dem source tells me, "and now we'll throw the rest of the house in too."

They cast themselves unashamedly as the pro-EU option for voters in West Oxfordshire in the hopes of being seen an outlet to protest against Brexit, and it paid off. The 19 per cent swing they secured propelled them from fourth last year to second, and they only need to go a bit further to win here. So it's no surprise that they'll double down on their pro-EU pitch in Richmond Park.

Tim Farron's troops have a lot of reason to feel confident in this campaign. Richmond Park is firmly Europhile territory, with estimates that as many as 77 per cent of residents voted to remain in the European Union. Approximately three times more people voted Remain in Richmond (75,396) than live in Witney (27,522). The local borough of Richmond upon Thames was the 20th strongest area for Remain in the referendum. The Lib Dems may be facing someone known for being an independent-minded Conservative, but that doesn't mean he is invulnerable.