Mandelson’s ability to get Nathan Rothschild, a Tory donor, to counter-attack Osborne over the “pouring poison” line is widely seen as a tribute to his powers of persuasion.

In reality Rothschild, who has long been enamoured with and in thrall to Tony Blair, acted after Mandelson got Blair to call Rothschild to encourage him to embarrass Osborne. M’learned friends are now being consulted as claim and counter-claim are spun. Isn’t it great to have all the fun of the circus with Mandelson back…

UPDATE : Tories say it was some time after the meeting that Rothschild called them to offer a donation on behalf of Deripaska. A Guido source laughed at the idea that Osborne and Feldman would personally solicit £50,000 – “that would get you to sit at the top table at a dinner maybe”.

CCHQ are calling Rothschild a liar:

The allegations made in Mr Rothschild’s letter are completely untrue.

Both Andrew Feldman and George Osborne deny absolutely that they attempted to solicit a donation from Oleg Deripaska. Nor did they suggest a method by which he could conceal a donation via a British company.

They spent a short period of time on Mr Deripaska’s boat at the invitation of Mr Rothschild. Donations to the Conservative party were not discussed with Mr Deripaska.

In a conversation on September 18, Mr Rothschild suggested to Andrew Feldman that Mr Deripaska wanted to make a donation to the party through one of his British companies. The offer was not taken up.

For clarity: the Conservative party has neither sought nor received any donations from Mr Deripaska nor any of his companies.

Looks like the lawyers will definitely be called in…