US private equity giant TPG has been sued by a jailed Russian oligarch in London’s High Court over a claim that the firm was involved in a conspiracy to seize or acquire his assets for below-market value.

Ziyavudin Magomedov has brought the nearly $14bn claim against US-listed TPG, according to 31 August court filings, alleging the firm’s involvement in a conspiracy to seize assets from him or to acquire them at less than their market price.