
The hood was forced to fork out the hush money in a bid to protect his £40million drug-smuggling racket.
McGraw, who helped flood Scotland with cannabis resin in the 1990s, believed his empire would be critically threatened by the mysterious blackmailer.
A plan to execute the extortionist was abandoned after McGraw learned he'd left evidence with his lawyer in case he came to harm.
Last night an underworld insider said: "Tam wasn't happy with the situation but had no choice if he wanted to keep the guy quiet.
"He was making so much from his business at the time, that was the priority for him."
At the time McGraw was running a scheme to smuggle cannabis resin on holiday coaches taking families from Glasgow's east end on trips to Marbella and Benidorm.
Floors in the buses were raised to hide up to three quarters of a ton of the drug - worth £1.6million - on each journey back to the UK. Couples, often using children as cover, were paid £5,000 to courier £450,000 to Spain to buy the drugs.
Within weeks of the scheme's launch in 1991, the blackmailer approached McGraw at his Glasgow pub, the El Paso.
Secrets of the operation had been leaked by cash couriers during a boozing session in the city days earlier. A leisure industry worker overheard them brag of McGraw's scam. He then gave the gangster a dangerous ultimatum - cough up or be shopped to police.
Our source said: "The guy went to Tam and told him he'd written everything down.
"He made it clear that if anything happened to him, a letter with all he knew would go from his lawyer to the police. That made the guy virtually immune from attempts to take him out."
He added: "Tam realised the guy would just come back for more if he was given a one-off payment.
"So he offered him a percentage of the value of each load plus the chance to use the bus to bring some of his own hash over. The blackmailer could have held out for much more but greed got the better of him and he went along with the deal.

"He made an average £2,500 each time the coaches came back to Glasgow plus whatever he sold his own hash for."
By 1997, when detectives smashed the scheme after the two-year Operation Lightswitch probe, the extortionist had raked in a share of around £250,000.
Cops intercepted one of McGraw's buses and seized the drugs.
More than 30 people were arrested and 11 men appeared at the High Court in Edinburgh in 1998 after the bust.
McGraw, who died from a heart attack in July 2007, aged 55, escaped jail along with seven other plotters. He walked free on a majority not proven verdict.
Three other gang members were given heavy sentences following the lengthy trial. McGraw's brother- in-law, John Healy, 51, of Cathcart, Glasgow, was caged for 10 years. He eventually served five.
Liverpudlian Paul Flynn, 37, was jailed for six years but died of a heart attack in prison in 2002.
Cash courier Graeme Mason, 51, of Carnwadric, Glasgow, was handed eight years. Seven others were either acquitted by the jury or told by the trial judge there was not enough evidence against them.
The extortionist, whose identity is known to the News of the World, is now a leisure trade executive. After falling victim to him, McGraw hired ex-Irish paramilitaries to tighten security.
This article has 2 comments
..LETS BE HONEST.TAM payed in bungs/information.THATS WHY.so if you listen to Ferris/Campbell/and co.Tam was an idiot.but the man was no idiot.[ive met him].and as far as i know [which is not much].he.. Tam was a stand up guy.
By james fulton. Posted October 31 2009 at 11:41 PM.
I want to know why the Strathclyde Police or even the PF have not made any attempt to get his £40 million ..he never did an honest day work in his life and neither did his wife ..so why do the powers that be ..ignore his fortune ..does she have some sort of special dispensation ?
By M. Posted October 25 2009 at 9:14 AM.