The US-based investor has ensured his holding is hedged by time-limited derivatives, limiting his exposure to a fall in the company’s share price as he pushes for a seat on the board next month.
Senior figures at the bank have become concerned Bramson could use that position on the board to push risky strategies with the safety net of his complex investment structure, according to sources.
The regulators are also understood to have their own issues with the nature of Bramson’s holding - part-funded by Bank of America - and attempts to muscle his way onto the board.
Barclays raised concerns over Bramson’s holding earlier this month in a robust plea to shareholders.
Outgoing chairman John McFarlane said Bramson’s holding was “misaligned” with other investors.
He warned Bramson’s presence on the board would “destabilising” and “destructive” to the bank and its shareholders.
Bramson, whose investment vehicle Sherborne Investors holds a 5.5 per cent stake in Barclays, has previously called for its investment bank to be scaled back.
After becoming frustrated that his concerns were not being acted on, he called a vote to force his way onto the board.
The head of Barclays’ investment bank Tim Throsby resigned last week amid a raft of leadership changes designed to give chief executive Jes Staley more control.
New leadership of the investment bank’s three divisions, banking, markets and corporate bank will now report directly to Staley.
The bank insisted the changes were not linked to Bramson’s advances despite coming less than five weeks before the crunch AGM vote.