Sir Martin Sorrell has revealed that he had keyhole surgery to remove a tumour in February and is undergoing further “preventative treatment”.

The 78-year-old advertising mogul, who is currently executive chair at S4 Capital, said he has made an “excellent recovery” following the tumour operation.

Sir Martin added in a statement that he is having further treatment over the coming months but is almost back to “business as usual”.

“My doctors have advised me that during this treatment, I should be able to work as normal most of the time, fully engaging with the company and our excellent executive team, although I have also decided to reduce my travel schedule for a few weeks,” he said.

“Thank you as ever for your continued support and let me know how to help you in any way I can.”

The businessman founded S4 Capital in 2018 and has rapidly grown the digital advertising specialist through a raft of acquisitions.

S4 currently employs approximately 8,900 people in 32 countries.

He launched the business after resigning from WPP, the FTSE 100 firm he transformed from a plastic basket maker into one of the world’s biggest marketing companies.

Sir Martin left the business after an investigation into allegations over his conduct.