Guarantees

Former deal-maker, who joined the auction house in 2016 with the acquisition of Art Agency, Partners, will leave on 31 December

Third-party auction deals have made some people very rich—but they may be bad for the market in the long run

Anna Brady, with additional reporting by Anny Shaw

Guarantees can be lucrative, but in the face of savvy competition, novices can get burnt when backing works as a third-party