Many of WPP's 200,000 staff will feel "liberated" after the departure of founder Sir Martin Sorrell, according to one of his most senior lieutenants.

Stephen Allan, boss of WPP-owned media buying agency Mediacom, said Sir Martin's energy would be missed.

But he added Sir Martin always had an owner's mentality about running WPP, which many employees didn't appreciate.

Sir Martin resigned as chief executive on Saturday after 33 years running the world's biggest communications group.

His exit followed an internal investigation into claims of personal misconduct.

Earlier this month it was disclosed that WPP had appointed a law firm to investigate claims of financial impropriety.

While Sir Martin rejected the allegation "unreservedly", he accepted "the company has to investigate it".

WPP's statement, released late on Saturday, said: "The previously announced investigation into an allegation of misconduct against Sir Martin has concluded. The allegation did not involve amounts that are material."

Announcing his resignation Sir Martin said WPP had been his passion, but it was in "the best interests of the business" to resign.

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Less than a week after Sir Martin stepped down, Mediacom's chief Stephen Allan told me: "Everything went through his hands and in many ways that was good - it meant he cared about everything.

"But when you have such a big empire which overall didn't do brilliantly last year, many bits of the business did.

"His downbeat assessment of the company's fortunes was unfamiliar to parts of the company that did really well," he added.

Sir Martin built WPP from a tiny shopping baskets manufacturer in 1985 to the world's biggest advertising company with revenues of over £15bn pounds.

Along the way he became the highest paid boss of a FTSE 100 company and amassed a personal fortune, getting paid £70m in a single year in 2017.

But also made a lot of other people rich along the way when he bought their businesses.

He gobbled up hundreds of firms and the geographical reach of WPP's interests made Sir Martin a "go to" guy when the media wanted a take on the world of marketing - often seen as a leading indicator of global consumer trends.

He was happy to oblige and journalists valued his willingness to comment and his unapologetic stance on issues - like pay - that other chief executives would have ducked.

He is one of the few UK chief executives that had a global standing and his relationships with WPP's key clients will be missed says Stephen Allan - but it's not a game changer according to the Mediacom boss.

"The truth is that we don't live in the world where a phone call from Sir Martin can seal the deal"

So, no one - not even Sir Martin Sorrell is indispensable? "I'm afraid not," says Stephen Allan.