But Hornby’s reign at Boots appeared trouble-free, with the group’s last set of results showing a 12.7% hike in trading profits and recent sales figures revealing that the high-street chain shrugged off a tough December which left many rivals under pressure.

The group stressed yesterday that it expects to deliver another year of strong trading profit growth when it reports results to March 31 in May.

Hornby said: “After an intense last five years as chief executive of two major companies, I have decided to take a few months break.”

He added: “I have thoroughly enjoyed the last couple of years at Alliance Boots during which time the company has performed very well.”

Mr Hornby also leaves behind a well-paid position, with an £850,000-a-year salary, not including bonuses.

He landed a £400,000 golden hello when he took on the top job at Boots in July 2009 and the firm’s last annual report showed he earned a total of more than £2m in pay and benefits for the first nine months alone.

The group will now begin the hunt for his successor, but it is thought there are two strong internal candidates – Alex Gourlay, chief executive of the health and beauty division, and Ornella Barra, head of the pharmaceutical wholesale division and long-term partner of Mr Pessina.

Pessina teamed up with private equity firm Kohlberg Kravis Roberts to take Boots private for £11.1bn in 2007.