JUST days after assuring us that they are virtuous chaps really - not bumping anyone off, nor spying on the royals - the Security Service was suddenly showing its sinister side.

For as former MI5 officer David Shayler was watching football on TV in a bar in Paris, apparently on the eve of being about to blab about what goes on in the secret world of state snoopers, he was whisked off to jail.

And there he might remain for months before finding out whether he will be extradited to Britain to stand trial on charges under the Official Secrets Act.

Clearly, his ex-employers are not happy at the notion of Mr Shayler sounding off.

But while it is inevitable that MI5 will resist having its activities compromised, one wonders whether the operation to shut up Mr Shayler has less to do with the interests of national security than it has to do with sparing the blushes of the Security Service.

For, noting that Mr Shayler may be a person with an axe to grind, having apparently quit MI5 in disappointment over his career prospects, what are we to make of his revelations so far - other than the no-big-deal disclosures that it kept files on Cabinet Ministers Jack Straw and Peter Mandelson?

The real substance of his so-far-veiled revelations - and of MI5's fears - is, it seems, that he worked with a lot of bunglers, whose errors and their effects he was poised to disclose in detail on the Internet...until they pounced on him in Paris.

Perhaps we shall never know the full tale or the strength of Mr Shayler's suggestions that MI5 is a byword for blundering.

But if its efficiency may be measured by the way they have kept tabs on him, we may sleep easy in the notion that our national security is in safe and competent hands - or that, at least, its damage-limitation department is.

Converted for the new archive on 14 July 2000. Some images and formatting may have been lost in the conversion.