As financial executives scramble for clarity on the new UK government's Brexit plans, Barclays has joined a small club of City firms that have hired a little-known consultancy with ties to the highest echelons of British politics.

The UK lender has become the latest financial institution to sign up for the advisory services offered by Hanbury Strategy, an unlikely partnership between Ameet Gill, the influential pro-Remain former director of strategy for Number 10 and a special adviser to then Prime Minister David Cameron, and Paul Stephenson, the pro-Brexit former communications director for campaign group Vote Leave.