Shell, the Anglo-Dutch oil giant, has drafted in leading mergers and acquisition bankers from Citigroup and Rothschild to advise on its structural review and refused to rule out a break up of the business.

The Citigroup team is led by David Challen, a vice chairman of the investment banking group, and includes Philip Robert-Tissot, a senior M&A banker, and Julian Mylchreest, European head of energy and power. Mylchreest is leading the team advising Russian oil group Sibneft on its demerger with rival Yukos.