In his 11-year tenure at the LSE, eight of which have been as FD, Howell played a key part in fending off takeover attempts from rival exchanges. Nasdaq, in particular, made repeated efforts to seize hold of the Exchange.

On leaving the Exchange, his shares may be worth £10m, after the share price soared in value following recent approaches.

LSE top brass believe Howell has been 'instrumental' in the delivery of exceptionally strong shareholder value, developing the Exchange's financial strategy and putting it to the forefront of the sector for balance sheet efficiency.

Howell will take up a role at fellow FTSE 250 company, Close Brothers. He replaces Peter Winkworth, who is stepping down after 30 years at the company.

Howell raked in a base salary and bonus of £972,000 during the LSE last full financial year, but could make double that amount at Close Brothers. Howell will start at Close Brothers in February 2008.