MOSCOW (AP) — Exiled tycoon and former prisoner Mikhail Khodorkovsky says revolution in Russia in inevitable.

Khodorkovsky, once Russia’s richest man, was pardoned by Russian President Vladimir Putin in December 2013 after spending ten years in prison. The charges of tax evasion and embezzlement against him have been seen as punishment for challenging the Kremlin and harboring political ambitions. Upon his release, Khodorkovsky left for Germany and has remained in exile.

Speaking Wednesday at a webcast conference in London, Khodorkovsky said Putin has driven Russia into a position when a “revolution is inevitable and necessary.” The tycoon said his task would be to help that revolution be peaceful. He would not say whether he would be helping opposition forces topple Putin.

Russian investigators sent a summons Monday to Khodorkovsky in a murder investigation.