A 63% surge in trading revenues at Barclays during the first half of this year has failed to convince its largest shareholder of the unit's value — activist investor Edward Bramson is renewing his push for an overhaul of the division.

In a letter to shareholders by Bramson's Sherborne Investors, seen by Financial News, the activist investor said that Barclays should follow Deutsche Bank in making a radical overhaul of its markets business in a bid to bolster returns to shareholders.