Graham's responsibilities will be taken on by Raffaele Jerusalmi, who will also continue in his role as head of the exchange's derivatives and fixed income business.

In a statement, the LSE says: "Raffaele's enlarged role is part of a streamlining of the senior management structure, which will now be organised around three core business units, namely Capital Markets, Post Trade, and Technology and Information Services."

Graham joined the LSE in 2003 as director of markets. In January 2008, following the merger with Borsa Italiana, he was appointed head of the combined groups' equity business.

His responsibilities included the junior Aim market and RNS, the LSE's regulatory news service.

Jerusalmi's expanded role will cover the same areas he led at Borsa Italiana before its acquisition.

Former Lehman Brothers man Rolet will begin his role as CEO in the next few weeks, taking over from Clara Furse who has led the group since 2001.