According to his publicly-available LinkedIn profile, Christopher Steele never existed before he co-founded Orbis Business Intelligence, a “corporate intelligence consultancy” providing “strategic insight, intelligence and investigative services”.

There is no mention of the 52-year-old’s life before 2009, when he and Orbis took up offices in Belgravia, one of the wealthiest districts in London, and indeed the world.

The man behind the explosive dossier on US President-elect Donald Trump is proving equally elusive in the flesh, as well as online. “Terrified for his safety”, he is reported to have driven from his home in the south of England having asked a neighbour to look after his cat because he would be “gone for a few days”.

Now, though, some sources have started to fill in the gaps in the secretive Mr Steele’s CV.

Said to be a father of three, it now appears he has an impressive intelligence gathering pedigree: a former MI6 officer posted in 1990 to the UK’s Moscow embassy under the guise of “second secretary (Chancery)”; working in the Paris embassy in 1998 as – supposedly at least – “First Secretary Financial”; at the Foreign and Commonwealth Office in London in 2003.

According to some reports, he may have worked with the murdered Russian spy Alexander Litvinenko, poisoned with polonium in in London in 2006 – by Russian state agents, according to a British public inquiry.

Some acquaintances describe Mr Steele as very sound and thorough, with an extensive range of useful contacts.

John Sipher who retired in 2014 after 28 years working for the CIA as a Russia specialist in Russia told the Wall Street Journal – the first news organisation to name Mr Steele – that he had a good reputation in the intelligence world.

The endorsements on that LinkedIn page would certainly suggest so.

His “intelligence analysis” expertise has been approved by Clovis Meath Baker, director of intelligence production at GCHQ from 2010 to 2013, with prior experience of working in Afghanistan during the Russian occupation and Czechoslovakia during the Velvet Revolution that ended communist rule there.

Other endorsements appear to come from Jonathan Winer, US special envoy for Libya, as well as from a retired British Foreign Office official.

Reuters has also reported that Mr Steele impressed with the work he did after leaving the British secret service. He is said to have provided the FBI with information on the activities of Fifa, world football’s governing body.

Emails seen by Reuters indicate that, in the summer of 2010, members of a New York-based FBI squad assigned to investigate “Eurasian Organised Crime” met Mr Steele in London to discuss allegations of possible corruption in FIFA.

The FBI squad whose members met Mr Steele subsequently opened a major investigation that led to dozens of US indictments, including those of prominent international football officials. Fifa president Sepp Blatter subsequently resigned.

The Independent has also established that Mr Steele had a more recent success with a report he supplied five months ago claiming that figures in Mr Trump’s campaign team had agreed to a Russian request to try and dilute the focus on its intervention in Ukraine. Four days later Mr Trump stated that he would recognise Moscow’s annexation of Crimea.

Not everyone, however, seems quite so convinced by Mr Steele, at least when it comes to his dossier – and not just Trump himself, who has angrily dismissed it all as “fake news”.

One source reportedly told The Times that Mr Steele was “slightly more showy and less grounded in reality than you might expect a former SIS [Secret Intelligence Service] person to be”.

“Not everyone was hugely impressed by him,” the source added, “But he has made a successful career for himself.”

There have also been comments in the intelligence community on basic errors in the dossier, like the misspelling of Alfa, one of Russia’s biggest and most prominent banking institutions as “Alpha”.

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And one business intelligence consultant with 20 years’ experience of Russia told The Independent that the dossier, with its extremely highly placed sources and lurid details, was simply “too good to be true”.

The source said: “Russians are very cautious about what they talk about, even amongst each other. Therefore, with the story about [sexual acts] in the Moscow Ritz Carlton, the idea you have managed to triple source it via an employee at the hotel, a serving FSB [Russian security service] officer, and the security officer at the hotel, who inevitably will be at least a former FSB or GIU [Russian intelligency agency] officer … It just doesn’t make sense.

“If such a thing had taken place, it would be a Russian state secret.”

“It’s just too magical,” the source added. “The specificity of the conversations about what is going on inside the Kremlin: nobody has this kind of detail.

“It would have meant that whoever was writing the report was far better than any British or CIA agent since the Russian revolution.”

The source also questioned the extent to which Mr Steele – a former MI6 officer who once worked in Moscow – would have been able to visit Russia in person.

“I would be surprised if he could go to Russia [himself],” the source said. “The Russians don’t believe you ever leave the intelligence services. I would imagine the Russian state would continue to be interested in someone who had served, particularly undercover in the embassy, and who knew where the British resources were in Russia.

“I’m told he would have had to ask permission [from the British Government] before going to a country like Russia.”

Instead, the source said, Mr Steele may have had to work through Russian subcontractors – who might have a financial incentive to please their paymasters with impressive-looking information, or who may have gossiped with other Russians keen to exaggerate the extent of their knowledge.

“I would imagine he worked through Russian subcontractors,” the source said. “We all [sometimes] work through subcontractors. Then we have to test the information they supply to us. And on a big case you should test the information more than you do on a small case.”

The source added: “I know there is a danger if you are doing a very big case and you are a small company, and you get something that seems really great, that you develop patterns of group think, and you start to believe your stuff – as happened for example with the Niger yellowcake story [that Saddam Hussein had tried to buy yellowcake uranium for nuclear weapons].”

The source, however, explained that it might be possible to reconcile Mr Steele’s apparent reputation for solid thoroughness with all the scepticism about the contents of the dossier.

It was, the source said, entirely plausible that as an ex-MI6 man Mr Steele may have been accustomed to supplying “raw intelligence” that was subsequently “stress-tested” by others.

“I am told this is what MI6 reports look like,” the source told The Independent. “In an organisation like MI6, people gather intelligence, another layer of people analyse it, another layer determines how good it is. Finally it is passed to the Foreign Office, who will do another layer of analysis to say whether it is real or not.”

Mr Steele is said to have been hired by an American political research company, and the ultimate intended recipients of his work are understood to have been political opponents of Mr Trump. “Sometimes,” the source added, “The client says ‘get me all the scuttlebutt.’”

Some news reports do seem to back up the suggestion that Mr Steele was supplying raw intelligence that was then subjected to further analysis.

CNN has reported that a two-page synopsis of Mr Steele’s dossier was only presented to Barack Obama and Mr Trump after US intelligence agencies checked the ex-MI6 man’s credentials and found him and his sources “credible enough to include some of the information”.

It is, however, not yet clear exactly what information made it into the two-page synopsis. Nor has anyone publicly said that any of the claims in the dossier have been verified.

Mark Galeotti, Senior research fellow at the Institute of International Relations Prague, has also raised one other problem with the suggestion that the Russians may have been gathering compromising information about Mr Trump that could have allowed them to blackmail him.

“The uncomfortable irony,” said Mr Galeoti, “Is that there is so much that is grotesque in his [Trump’s] backstory, behaviour and even personal narrative, which did not prevent his election, that he might even be immune to this kind of blackmail.”