Hornby, who stood down from his post of chief executive at Alliance Boots in March after less than two years, is said to be focusing on breathing new life into the Coral bookmaking division.
The post had been vacant since Nick Rust left to join Ladbrokes a year ago following a restructure at the company.
Hornby started at the company this week. He takes on responsibility for Coral’s online and telephone betting business as well as its national high street chain.
The former Asda executive takes up the post following a break from ’an intense last five years’ after leaving Alliance Boots. Hornby was chief executive of HBOS in 2008 when the bank nearly collapsed under the weight of £11bn losses.
He previously held a number of senior roles at Asda including marketing director.