Sherborne Investors, the activist investor controlled by Edward Bramson, has nearly tripled its stake in 3i Group, raising expectations of a showdown with the UK private equity firm.

Sherborne Investors B - a £200m vehicle raised by Sherborne Investors Management last year to buy up to 30% of a listed undervalued company, said in a stock exchange statement today that it now holds 40.8 million shares in 3i Group. This represents a 4.3% stake in the private equity firm and means that the vehicle has nearly tripled its ownership of the company within a month. It first revealed it had bought a 1.6% stake in the FTSE 250-listed firm on January 29.