Mr Stalker was hired by HarperCollins to protect Baroness Thatcher's memoirs ahead of their much-hyped publication next Sunday. He need not have bothered: yesterday's Daily Mirror had some of the best bits spread over five pages.
At Wapping, where the Sunday Times was preparing for publication of extracts at the weekend after paying pounds 200,000 for serialisation, the mood was one of anger and dismay. How had the Daily Mirror stolen its thunder?
The author of the Mirror article was not saying. Whether he had a copy or had seen a copy or knew someone who had - David Seymour, the Mirror Group political editor, was remaining tight-lipped.
All he would say, enigmatically, was that 'an awful lot of people have seen the book' and he had been 'working on it for some time. It was not a five minute job'. And in a dig that would give Andrew Neil, the Sunday Times editor, and his cohorts palpitations, he added: 'I've heard the Sunday Times plans to spend pounds 450,000 on advertising. If so, we've done them a favour. They should cancel it now.'
Mr Neil, untypically, was saying very little. His executives were more chatty and were quick to hit back in true Fleet Street tradition. They did not know if the extracts were genuine but they did know that one of their staff had been offered pounds 10,000 for a look and that sums of between pounds 10,000 and pounds 50,000 from cheque- book toting hacks had been mentioned.
Whatever the truth - and they were able to offer no proof to substantiate their claim - there was no denying the Mirror its scoop.
Also locked in discussions with their lawyers were executives at HarperCollins. They paid pounds 3.2m for two volumes of memoirs, of which this, The Downing Street Years 1979-90, is the first. Even by the sometimes crazy standards of publishing, this was a massive sum. The book will cost pounds 25 and HarperCollins will have to sell 150,000 of the initial print run of 200,000 to start making a profit.
To protect their investment, they hired Mr Stalker to oversee security at the company's Glasgow printing plant and warehouses; and people who were shown the book in advance were made to sign non-disclosure letters.
To no avail. For just 27p the bits that most people would like to read and the Government would rather they didn't, were available on the news stands.
Asked whether Mr Stalker had a new job, trying to catch a mole, a HarperCollins executive was silent. One name can be ruled out, straightaway. Jeffrey Archer had been offered a copy but refused to sign for fear of being compromised.