Wippell has advised on some of Ashursts' biggest corporate deals in recent years – and his departure is believed to have shaken the firm more than last month's departure of four banking partners, led by Stephen Mostyn-Williams, to US firm Shearman & Sterling.
In 1996, Wippell led teams advising Lloyds Chemists on Unichem's £514m bid and five months later insurer Sun Alliance on its £6bn-plus merger with Royal Insurance.
This year he advised five insurance companies, including the Royal & Sun Alliance, on its investment in the £950m buy out of insurance broker Willis Corroon.
It is believed he may have been disappointed when Ashursts rejected a merger offer from Clifford Chance earlier this year.
His move is further evidence of an aggressive period of lateral hiring by A&O, which in the last six months has taken on three asset finance partners from Wilde Sapte and a tax partner from Herbert Smith.
Neither Ashursts nor Wippell would comment on the move. A&O's head of corporate Guy Beringer said that the firm was “clearly pleased”.