Simon Mann, 'we can use mercenaries to defeat ISIL

Yet if there is one thing that the bickering generals and politicians could probably agree on, it is that whatever the solution, none of them will be asking Mann to provide it. This after all, is the fellow who ended up being sentenced to 34 years in Equatorial Guinea's Black Beach prison, after his 2004 plot to overthrow the country's dictator, Teodoro Obiang, was rumbled in advance.

As "banged up abroad" predicaments went, it made Midnight Express look like a holiday. And as his many critics were quick to point out, the plot he had tried to hatch seemed so improbable it sounded like a badly-written thriller. Not only had he enlisted as a financier, Lady Thatcher's son Mark (who has always denied any knowledge of the plot and only admitted to breaking anti-mercenary legislation in South Africa by agreeing to charter a helicopter) - never the best option for keeping things low-profile - news of the plan had leaked out months before.

Mann pressed ahead, convinced he had the tacit backing of Western intelligence, only to be arrested with 69 others during a weapons pick-up in Zimbabwe, which then obligingly extradited him to face Obiang's tender mercies in Equatorial Guinea. To the surprise of many, he was pardoned on 'humanitarian grounds' in 2009.

Yet despite his contribution to the mercenary trade's long history of infamy - a subject on which he is now writing a book - the reason the coup backers came to Mann in the first place was because he had a very good record at what he did. His previous firm, Executive Outcomes, halted rebel movements in their tracks in both Angola in 1993 and Sierra Leone in 1995, the latter against the drug-crased, limb-chopping rebels of the Revolutionary United Front. On both occasions it was in support of legitimate governments, and while some may have questioned the millions they were paid, nobody ever doubted their effectiveness.

Indeed, in person, it is hard to recognise him as the forlorn figure that he cut at his trial, sitting handcuffed in a courtroom in Equatorial Guinea's sweltering capital, Malabo. The scraggy beard is gone, and in place of the prison fatigues is a smart pinstripe suit that is more City banker than soldier of fortune. He comes across as charming and thoughtful, and while he still works as a security consultant, much of his time since his release has focused on writing and promoting his memoir, Cry Havoc.

Yet earlier this year, one of his old South African partners, Colonel Eben Barlow, was back in action, this time fielding a force of fighters to help Nigeria defeat the Islamists of Boko Haram. As the Telegraph reported last month, the group spent three months fighting alongside the Nigerian military, bringing with them years of hard-won experience in South Africa's apartheid-era bush wars. They had only around 100 men on the ground, but even in that brief time, they turned a demoralised and badly-led army into a fighting machine that finally pushed Boko Haram from its north-eastern strongholds.

With many of their men recruited from South Africa apartheid-era security forces, neither Nigeria nor the wider world has been keen to fete this achievement. But the fact remains that a group of mercenaries - or, to give them their polite name, a private military company - has succeeded in defeating one of the world's bloodthirsty insurgent groups, partly through sheer dint of being willing to put boots on the ground. Britain and America, for all the help that they offered Nigeria's army after last year's schoolgirl kidnappings, refuse to work alongside it because of its human rights record.

So could they be used in similar fashion to defeat Isil? After, all there a few parallels between the situation in Nigeria and that in Iraq. Once again, a fanatical Islamist group is getting the better of a lousy national army, as evidenced by Isil's capture of the Iraqi city of Ramadi last month. And once again, the West is wringing its hands about the situation, but still unwilling to put troops directly in the line of fire.

According to Mann, the answer is "yes". First off, he says, any successful strike force would need back up from airpower and armour, just as EO's private armies in Angola and Sierra Leone used. Those, however, are already within the Iraqi army's reach. Otherwise, he argues, it is simply a question of building the necessary esprit de corps. "I would form a kind of Arab Legion, just like the British did in the old days" he says. "With the right training, probably a minimum of two months, you can turn pretty much anyone into good troops, as long as you have good officers and good NCOs.

"After all, if you are a soldier and you are about to go into battle, what goes through your mind? Firstly, you are sh**ing yourself. And secondly, you have to know that you are going to win. No one wants to die pointlessly. If you have a corporal who is telling you, 'I am behind you, I am not going to let you die', that makes a crucial difference."

But would that be enough against Isil, whose very willingness to die in battle is their best weapon? After all, in last month's battles in Ramadi, one of the things that drove the Iraqi Army to flee was legions of suicide bombers, some driving explosive-rigged armoured trucks impervious to gunfire.

"Don't get me wrong, Isis are probably very frightening up front, although I doubt they are as professionally trained as the rebels we came up in Angola," says Mann. "Yes, I too would be scared if they come hurtling towards me with an exploding armoured truck. But it still doesn't do anything like the damage that a main battle tank can, and it isn't that difficult to stop a truck with two tonnes of explosives on it. You can build a ditch, for example."

As it happens, Mann says, word has reached him on the PMC grapevine that various firms are already in contact with the Iraqi government, offering ancillary services like help with analysing intelligence data. That, though, is like the private sector offering do hip replacements instead of the NHS. Hiring them for the much bloodier surgery needed to remove Isil altogether is another question entirely, not least because of the politics involved. To many in the West, and even more in the Arab world, the notion of fighting Isil for profit rather than principle would be hugely controversial.

Then again, Mann insists neither his earlier ventures nor the Wonga coup - named after a "Wonga List" of coup found by South African police - were ever just about the "wonga". On all three occasions, he claims, he also believed in the rightness of the mission itself. In Angola, he helped government troops defeat rebels who had seized the country's main oil port in violation of a peace treaty. In Sierra Leone, he stopped the RUF carrying out even more massacres than it had done already. And in Equatorial Guinea, where a group of "Barrel Boys", or oil men, asked him to topple Obiang, he says he only agreed because he thought the leader lined up to replace him would be less of a tyrant.

True, in the parts of the world that have called in Mann's services over the years, the line between good leader and bad is often rather blurred anyway. But in Cry Havoc, he insists that wherever he went, part of the idea was to "improve the lot of the Mr and Mrs Bloggs of the country we were in".

For all that, though, he says that if British and American warriors do end up going back to Iraq, he would rather it was as part of regular armies rather than as private soldiers. "I may have been one of the founders of Executive Outcomes," he says. "But as a matter of principle, I would rather governments were involved where possible."

So what, then, if Britain and America continue to refuse send in troops to Iraq? If he got a call to help Mr and Mrs Bloggs of Baghdad, would he take it on? He grins. "I might do. Although this time, I would talk to people in authority first."