LONDON — The senior official credited with helping sort out the UK Ministry of Defence's broken finances is leaving his post as permanent secretary to head up the country's tax department.

Jon Thompson has been was the top civil servant at the MoD since his appointment in September 2012 as Permanent Under Secretary. Previous to that Thomson was previously director general of finance at the department.

The official, who has responsibility for MoD finances, reform, strategy and other roles will move to become chief executive of the Ggovernment’s revenue and custom’s department, the HMRC.

A replacement has yet to be named for the defence department job.

Defence Secretary Micheal Fallon said Thomson had "played the key role in helping to sort out the department’s finances and balancing its budget in addition to overseeing important organisational change and the delivery of last year’s Strategic Defence and Security Review."

Thompson has been central in helping balance the books at a department previously ridiculed at the Treasury for it's inability to manage it's own budget.

The official was at the heart of efforts to eliminate a £38 billion black hole in unfunded commitments at the same time as the defence department was wrestling with an 8 percent funding cut as the Conservative-led coalition Ggovernment sought to repair public finances post 2010. 

"Thompson is an able accountant and genuinely decent man brought in as finance director from outside the MOD. He gained ministers' respect and trust by ruthlessly eliminating the so-called black hole. He was the obvious choice to consolidate the good work from the top when the Permanent Under Secretary job became vacant," said one former Government official.

The official, who asked not to be named, said that reforms introduced into the MoD over the last few years had watered down the position of the department's civil service head, a trend that needed to be reversed..

"We now need a Permanent Under Secretary with real power who deeply understands defense, deterrence and international security and who, while strongly supportive of the military, is not overawed by them or short termist politicians. Thomson had the respect of the military and his successor will too," he said.

Sir Peter Luff, a former defence procurement minister who worked closely with Thompson in the Conservative-led coalition Ggovernment which came to power in 2010 said he had been was "A highly influential figure, for better and worse. A very tough figure,which the department desperately needed."

"I didn’t always agree with him. Sometimes he took a very numbers-based approach. But he was a key component in the transformation of the department’s finances. Crucially, he also won the credaibility of the Treasury," said Luff.

"It's uncontestable he has left the MoD in a much better place than he found it. He seems to have been the right man for the right time. Now though times are a little more normal, we may need a different style of Permanent Under Secretary and a more traditional role," said Luff.

Andrew Chuter is the United Kingdom correspondent for Defense News.

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