Col Collins, a father of five, was eventually exonerated, promoted and awarded an OBE.It is thought that last week Army chiefs tried to prevent his embarrassing resignation, offering him a favourable future posting. Col Collins is currently a staff officer at the headquarters of the UK Land Forces in Wiltshire.
As the former operations officer for the Special Air Service, having completed the Staff College course and with operational command of a regiment, Col Collins was destined for the top.
At the very least it is likely that the colonel would have been offered the brigadier's post of Director Special Forces (DSF) in charge of the SAS and the Special Boat Service. The position would have inevitably led to Col Collins's promotion to general.
An Army friend said Col Collins's wife and family "had had a torrid time" during the Iraq investigation. "His family found it very hard to take," he said. "Events went from the extremes of high praise to vitriol.
"There were a lot of colleagues running away from him and only a few running towards him. Tim certainly discovered who his real friends were. People distanced themselves to make sure they were OK until he was cleared."
A military colleague, who said the resignation came as a shock, believed that the officer stood a very strong chance of becoming DSF and that in no way had his career "come to the end of the line".
As the commanding officer of the 1st Bn the Royal Irish Regiment, Col Collins made an inspirational eve of battle speech.
The text of the speech was later framed and hung on the wall of the Oval Office by President George W Bush and praised by the Prince of Wales as encapsulating all that was good in the British Army.
Surrounded by his troops, the cigar-smoking, officer said: "If you are ferocious in battle remember to be magnanimous in victory."
The colonel, who was nicknamed "Nails", urged his men to wrap their fallen comrades in a sleeping bag, fight on and grieve for them only after the heat of battle.
The Ministry of Defence confirmed yesterday that Col Collins had put in an application for resignation last week that would by approved by an Army board within 12 months.
A family friend at his mother's home in Belfast, where Col Collins was born and educated, said she was not surprised that he had resigned because of the unwarranted Iraq investigation.
"It's the Army's loss," she added.
After 22 years devoted to serving his country Col Collins will leave with a pension and an opportunity to seek fresh employment in the civilian world.
Friends said he might take up book offers, go on the speech circuit or enter the security business.
Everyday someone says The Passion is about Christians and Jews, but it is really about everyday events where cowards and backstabbers are exposed and honest people find out who are their friends. 2000 years of history does not change much about human nature.