The agency is providing media PR support for PCP Capital - the investment firm that brokered Sheikh Mansour Bin Zayed Al Nahyan's bid to take a 16 per cent stake in the UK bank.
David Bick, chairman of Square 1 Consulting, is understood to have met Ali Jassim, adviser to Sheikh Mansour, and PCP's Amanda Staveley to discuss the media strategy.
Media interest in the deal has been intense, particularly as Staveley, a former model and ex-girlfriend of Prince Andrew, has reportedly made £40m for PCP from the deal. The Times described her as the City's 'golden girl'.
Square 1 Consulting has an existing relationship with the various players, having been involved in the sheikh's recent takeover of Manchester City, also brokered by Staveley.
Existing shareholders, though, are reportedly angry that the terms of the deal seem inferior to what was on offer from the UK Government and are yet to approve the deal.