He officially stopped work as press secretary to ex-transport minister Stephen Byers only three weeks ago. Since then, he has been working in a more familiar guise - as a journalist - for Channel 4, on a documentary about the history of Whitehall and special advisers.
'Channel 4 is talking about putting it out in September, the political conference season,' he says with a smile, hinting at the acrimony that surrounded his departure from the DTLR. Relations had broken down between him and Byers, and eventually Byers announced Sixsmith's resignation before the latter had agreed to resign.
Since then, Sixsmith has been on the receiving end of some serious allegations. His critics claim he is responsible for the downfall of Byers and that he tried to undermine Byers and adviser Jo Moore (whose infamous e-mail suggested 11 September was 'a good day to get anything out we want to bury'). Others say that since being suspended on full pay, he has tried to sell the inside story on Byers to the papers. He declines to comment on these allegations, and refused to talk in detail about his time at the DTLR.
Now he has left the department, his work still courts controversy. He claims in this interview - his first since leaving government - that his show for C4 has faced problems: 'The Government has been incredibly obstructive.
They have issued blanket instructions to ministries that they must not co-operate with this documentary.'
A Cabinet Office spokesperson denies this, saying: 'We have assisted the production company in their enquiries to date and are still in communication with them.'
Whatever the actual nature of the Government's help for Sixsmith's current project, he has clearly burned his bridges in Whitehall and has no plan of a return to the civil service.
There is an irony in the fact that this part of his career should end on such a note, since one of his first career choices when he left Oxford in 1980 was with the Foreign Office. His fluency in Russian and French, acquired from school, university and then the Sorbonne in Paris and Leningrad Polytechnical Institute, seemed to direct his career overseas. But this was not something that he planned: 'My career has progressed by random events,' he says, explaining how his news editor on a BBC trainee course was simply looking for 'someone who could speak French'. When Sixsmith raised his hand, he was offered a Brussels posting.
From the start, he says, he believed himself more suited to academia than journalism, having briefly taught Russian poetry at Harvard University after his first degree. His first experience of journalism prior to the BBC was a stint editing Oxford University's paper, Cherwell, four years earlier. From the BBC traineeship, Sixsmith went on to one of the most successful careers in TV journalism.
Between 1982 and 1997, he worked as a BBC foreign correspondent in Brussels, Geneva, Warsaw, Moscow and Washington. Stories he covered included the collapse of the Soviet Union in 1991 and the election and first term of US president Bill Clinton.
But after 17 years in journalism, he returned to the UK in 1997 and his first foray into PR as press secretary for the then Secretary of State for Social Security, Harriet Harman. This was followed by a year in the same role for Alistair Darling at Social Security - periods that he describes as 'wonderful times'.
'In 1997 there was a great feeling of renewal,' he says of wanting to work for New Labour. 'It was a good time to be in government information.
It was the first Labour government for 18 years, they came in with a lot of bold ambitions and a lot of that's been forgotten because of the travails of the past few years.'
He says his decision to return to the UK in 1997 from 17 years overseas was driven by a mixture of the needs of his four children ('who always said they were British but only knew this country as a place for holidays'), and a desire to leave behind the life of a foreign correspondent. Change has been thrust upon him this time, having 'been resigned' from the DTLR.
While he has no plans as yet for what he will do after September, he consider himself very much a communications person - and confirms he has been in talks with consultancies keen to offer him a job.
1988: Moscow correspondent, BBC
1997: Director of comms/press secretary to Harriet Harman
1999: Director of external comms, Marconi
2001: Director of comms/ press secretary to Stephen Byers