Mr Hollobone holds the record of the most rebellions against a party whip so far this Parliament, but he insisted that he would not be defecting. Mr Holloway did not respond to messages.
The terrace, running along the bank of the Thames, is packed in the summer months with MPs enjoying drinks from subsidised bars.
It was at the centre of allegations of sexual impropriety by MPs who had over-indulged.
Mr Richardson, a bon viveur in his early thirties, is also understood to spend several afternoons each week drinking coffee beneath the glass atrium of Portcullis House, the MPs’ office block, in order to approach potential defectors.
He is thought to have triggered panic in Tory ranks after boasting to targets of the number of Conservative MPs he had lined up to follow Douglas Carswell, the MP for Clacton, in quitting.
At Oxford, Mr Richardson studied engineering and was Treasurer of the Union. He made headlines as a student after he bluffed his way to China to deliver a series of lectures on economics at Beijing University, despite having no knowledge of the subject.
He was mistaken invited to speak on the course, and only gave up after nine hours of lectures, when he ran out of material from pages ripped out of an A-level text book.
Mr Farage is understood to have endorsed the operation but was incandescent after it came to light, threatening to “kick him in the b—s.” Mr Richardson declined to comment.
On Friday Mr Carswell was cheered by Ukip activists in Clacton, as he warned the “full weight of the Westminster machine” including Cabinet ministers been sent to hold the seat for the Tories.
Senior Ukip sources admit that no further defections are likely until Conservative and Labour MPs see the result of the Clacton by-election on October 9.
One senior figure said that by setting a precedent of calling a by-election after quitting, Mr Carswell may have “set the bar too high” and discouraged others from following suit.
On Friday Mr Farage said that he does not expect to be the leader of Ukip in ten years’ time. He suggested his successor would be a woman, saying Ukip is more likely to adopt a female leader than any other party.
Suzanne Evans, the party’s communities spokesman, is thought by members to be a front runner. Told about Mr Farage’s comments, she laughed before adding: “Leadship is a heck of a role.”