He replaces Don Cruickshank, and will take a massive salary cut in his new role.
A former managing director at BP, Gibson-Smith earned a package in the region of £2.8m, but can expect a salary of £250,000 for his two-day-a-week non-executive role.
Prior to his appointment to the LSE, Gibson-Smith was chairman of Nats, the air traffic control service.
Harrison Beale & Owen will (HB&O) have a new chairman and managing director at the helm for 2017
Satvir Bungar promoted to managing director in the mergers and acquisitions team
Carolyn Brown appointed as the first head of client legal services practice RSM Legal
UK senior partner Phil Verity has been elected for a second term at Mazars