The London Stock Exchange Group has set the date for a showdown with an activist investor calling for the resignation of its chairman, in the latest stage of a power struggle engulfing a company that is an emblem of the City of London.

Standing by the board's decision to call an end to Xavier Rolet's eight and a half years as chief executive, the LSE said that removing chairman Donald Brydon would be "destabilising", as well as "detrimental" to choosing a new CEO.