Embattled UK security giant Serco has appointed Aggreko boss Rupert Soames as chief executive. He replaces Chris Hyman, who stepped down after 11 years at the company in October 2013.

In a statement, Serco said it is focusing on rebuilding its business after A British government investigation found that it, and rival G4S, had wrongfully charged for work that was not carried out.

This included charging the Ministry of Justice (MoJ) for tagging criminals who were dead, still in prison, or where no tag had actually been put on the offender.

Soames will take up the post as of 1 June this year and interim leader, Ed Casey, will continue to lead the company in the meantime.

"It is has been an extremely difficult decision for me to leave Aggreko after 11 enjoyable and successful years," said Soames, who is also the brother of former Conservative Party government minister Nicholas Soames.

"I am hugely excited to be joining Serco as I have always admired the services it delivers and the passion and commitment of its people.

"I am aware that the company has experienced significant recent difficulties but the work that Serco does is important to the lives of millions of people and I believe that we can find a way through to a bright future. I am greatly looking forward to working with my new colleagues to deliver the quality of services that will impress our customers, shock our competitors and please our investors."

As well as the fraud probe, outsourcing giant Serco has wrestled with poor first half results in 2013 and the government's threat of a moratorium on public sector contracts.

Hyman's resignation followed that of rival Richard Morris at G4S, who was the Serco rival's UK chief executive.

G4S is caught up in a similar probe by authorities over one of its contracts with the Ministry of Justice, where it is accused of charging taxpayers for the tagging of prisoners when the work had not taken place.

"I have always put the interests of Serco first. At this time, nothing is more important to me than rebuilding the relationship with our UK government customer," said Hyman in a statement at the time.

"In recent weeks it has become clear to me that the best way for the company to move forward is for me to step back.

"I have been fortunate enough to have had the privilege of working at a great company with extremely talented people. I wish everyone at Serco the very best for the future."

Who is Rupert Soames?

Soames is currently the chief executive of Aggreko.

Aggreko is a FTSE100 support services company and world's largest temporary power generation and temperature control services business.

He has led Aggreko since 2003, serving customers, including many central and local government clients, in 100 countries around the world.

The services that Aggreko provides are often mission-critical, large and complex, such as supporting an entire country's national grid or successfully providing power to the 2012 London Olympics.

Rupert Soames is also currently the Senior Independent Director of Electrocomponents, the FTSE250 support services company.