Forces under his command reoccupied the Crater district of Aden which had been taken over by local police mutineers in what became known as "the last battle of the British empire".

In 1989 Mitchell took a leading role in the Halo Trust, a not-for-profit organisation undertaking mine clearance in former war zones.

Mitchell (Snr) worked in a solicitor's office and for the MacBrayne ferry company before serving in the 10th Battalion Argyll and Sutherland Highlanders in World War I. Mitchell (Snr) achieved the rank of captain (commissioned 'in the field') and was awarded the Military Cross at the Second Battle of Ypres, but when the young Colin asked him how he would only say, 'Oh, shooting rabbits'.

The family lived in a modest semi-detached house and Colin would attend services at the local Presbyterian Church wearing a kilt.

During Operation Agatha, which saw most of the Jewish political leadership in Palestine detained, Mitchell's mission was to arrest Moshe Shertok (a future Prime Minister of Israel).

[4] After recovering from his injuries, he was transferred from his regiment to become aide-de-camp to General Gordon MacMillan, the commander of British forces in Palestine and Transjordan.

Mitchell was placed in charge of the coastal towns of Paphos and Ktima, where his men engaged in counter-insurgency operations against EOKA guerrillas.

Soon afterward, he saw action in Zanzibar with the KAR in breaking up disturbances between the island's Arab and African populations, which had begun during a general election and had descended into widespread rioting and clashes.

At the time, Somali guerrillas were launching raids as part of a campaign to unite the region with Somalia, and the frontiers with other neighbouring states were also volatile.

Mitchell's familiarity with the Scottish clan system made him more comfortable with African tribal issues than was the case with his English contemporaries.

Mitchell was promoted lieutenant in 1947,[9] captain in 1952,[10] major in 1959,[11] and his success in a wide range of appointments won him brevet rank as a lieutenant-colonel in 1964.

[12] Mitchell was promoted to substantive lieutenant-colonel on 31 December 1966,[13] and made Commanding Officer 1st Battalion, The Argyll and Sutherland Highlanders (the 'Argylls') on 12 January 1967.

In late June 1967 the 1st Battalion Argyll and Sutherland Highlanders was due to take over responsibility for security in Aden's Crater district from the Royal Northumberland Fusiliers.

Three men from the Argylls (its Officer Commanding 'D' company, along with two privates) were killed when a patrol of the Royal Northumberland Fusiliers that they were accompanying was ambushed.

[17] Mitchell subsequently used what were described as "strong arm methods" to maintain order in the Crater district for the remaining months before British withdrawal from Aden.

[18] Mitchell then used an integrated system of observation posts, patrols, checkpoints and intelligence gathering to maintain the Crater as a pacified area whilst security conditions elsewhere in Aden began to deteriorate.

[18] Mitchell used the Chartered Bank building in the Crater district as his headquarters, and army snipers positioned upon its roof would shoot at anyone thought to represent a threat in the streets below.

One High Commission official in Aden describing the Argylls as "a bunch of Glasgow thugs" (a statement for which he later apologised).

The situation that developed was described in The Times as follows:[21] Mitchell frequently appeared on television: a small, handsome man with a direct, pugnacious manner, speaking the robust, un-minced words that the British had not heard from their army officers since the acceleration of the Imperial decline had begun nearly two decades before.

Tam Dalyell (Labour, West Lothian) asked whether it was true that: "Mitchell disobeyed operational and administrative orders of his senior officers during the recapture of the Crater"?

The nature of this rebuke was explained by British Government's Defence Minister Denis Healey as follows:[23] … the brigade commander thought it necessary to emphasize to Colonel Mitchell that the maintenance of law and order with minimum force leading to an orderly withdrawal from Aden with minimum casualties was the policy that had to be followed.The final British withdrawal from Aden took place in November 1967.

Interviewed by the BBC in 1985, General Tower said "Colonel Mitchell, for reasons of his own, wanted to cut a dash with the Argylls in the Crater" thereby accepting unnecessary casualties.

[26] Once he was a civilian, Mitchell assumed a prominent public role in a "Save the Argylls" campaign to stop the abolition of the regiment.

He published a memoir entitled Having Been a Soldier, undertook some freelance journalism and briefly took a job as management trainee with Beaverbrook Newspapers.

[32] He left Parliament at the time of the February 1974 general election, against the advice of both his wife Sue and fellow maverick M.P Tam Dalyell.

He applied to several constituency Conservative Associations, including Bournemouth East in August 1977, but at every selection interview the question was raised as to why he had given up Aberdeenshire West in 1974.

He is quite at odds with the world in which he finds himselfDuring this period Mitchell remained sporadically active in a series of consultancies, mostly of a military or security nature.

[8] In November 1980, Mitchell praised the Mujahideen as "gallant fighters... expressing themselves, as Afghans know best, in the romantic tradition of sniping, raiding and brigandry."

Once a popular member of the Garrick Club, he avoided it for years, finally stopping his subscription.In 1989, Mitchell co-founded the Halo Trust (the hazardous areas life-support organization).

It employed a core of (mostly British and Commonwealth) de-mining experts and a large number of locally recruited and trained personnel.