Britain has a debt of honour to pay in Sierra Leone

'Who gave the delightful Foday Sankoh his military training? You guessed it: Britain'

Perhaps it was all the fault of a good lunch. How else do we explain the behaviour of the British commander who led his men into the arms of the West Side Boys? There they were motoring back to base after lunch with Jordanian UN troops when the major took it on himself to do a little bit of bundu-bashing (for the uninitiated, this involves white men racing through the African bush in four-wheel-drive vehicles. They make a lot of noise and feel as if they are taming nature. So I've been told).

Perhaps it was all the fault of a good lunch. How else do we explain the behaviour of the British commander who led his men into the arms of the West Side Boys? There they were motoring back to base after lunch with Jordanian UN troops when the major took it on himself to do a little bit of bundu-bashing (for the uninitiated, this involves white men racing through the African bush in four-wheel-drive vehicles. They make a lot of noise and feel as if they are taming nature. So I've been told).

Major Alan Marshall is in disgrace this morning, awaiting the verdict of the formidable Lieutenant-General Sir Mike Jackson, commander-in-chief of UK land forces. The commander-in-chief is a man respected for his common sense. He might reasonably take the view that Major Marshall - for all the trouble and anguish he has caused - has suffered enough. I hope so.

The major is part of a fine British military tradition in Africa. I think of old Lord Chelmsford, who divided his force before the battle of Isandlwana. You just keep an eye on Johnny Zulu, chaps, and I'll head on with the rest of the men. Result, the slaughter of all but one of the unfortunate troops left behind to face the wrath of the Zulus. The British staged a comeback soon afterwards at Rorke's Drift, but Isandlwana was, to borrow the phrase used later in the Boer War, "no end of a lesson".

And as for the Boer War? A catalogue of military blundering that shamed even the generals. Lots of individual heroism all round and a kind of victory in the end, but it began disastrously. Major Marshall isn't remotely in the league of Lord Chelmsford or Redvers Buller, the benighted commander in the South African War, but he has earned himself a small place in history.

The rescue was spectacular, the most breathtaking military operation of its kind since the Israelis descended on Entebbe to free their hostages nearly 30 years ago. The capacity for these things to go wrong is enormous; just remember the Munich Olympics and the American rescue helicopters colliding in the desert of Iran. To be ordered to attack two well-guarded positions through swamp and jungle and emerge with your hostages alive... It is hard to imagine a more difficult mission.

But the right, from which one might have expected the loudest cheering over this derring-do, has been restrained, even sullen. It wants British troops pulled out of West Africa. Nothing to do with us. Let the UN sort it out. Some even whisper darkly about a British Vietnam. Well, on that score there is one major difference. The Americans found themselves entangled in the mess created by French colonialism in Indochina. We are entangled in a mess that is the direct consequence of British colonialism. A mess of our own making. A little reflection on history might help to jog our moral sensibilities.

As for the recent history, a couple of facts are in order. Who gave the delightful Foday Sankoh, chief butcher of the Revolutionary United Front, his military training? You guessed it: Britain. Who (in concert with the UN and the US) pressured the democratically elected government of Sierra Leone to accept a power-sharing government with the loathsome Mr Sankoh and numerous other killers? Britain, of course.

The appointment of Mr Sankoh as the minister in charge of diamond mines was one of the most cynical moves in the history of Western impositions on Africa. Mr Sankoh's army of mutilators and rapists ran its war with the profits of the mines. What do you give him for agreeing to peace? Control of the diamond mines, of course. Inevitably, the whole peace deal fell apart. The rebels were never sincere and the UN force sent to implement the deal was incompetent and ill-organised. Had it not been for the intervention of British paras and marines last May, the butchers would have been back in power. I was in Freetown when the rebels were beaten back the previous year, and saw the almost hysterical joy of people as a small detachment of Royal Marines patrolled a village on the front line.

I would recommend that the opponents of Britain's involvement should ponder the words of Thucydides, from The Peloponnesian War: "We have come as allies to those of you who are being oppressed; our help was asked for, and we have not arrived uninvited."

The French offer the most obvious comparison with the British operation in Sierra Leone: white armies imposing order where the locals had failed. But this intervention isn't remotely comparable to the adventures of the French in Central Africa. They sent paras and legionnaires to aid despotic regimes in Zaire, Central Africa and Rwanda. The result was the moral catastrophe of Rwanda: a French-armed, French-trained military directed a genocide that led to the deaths of a million people. And when French troops were sent into Rwanda at the height of the slaughter, they went to provide a safe haven for the murderers.

The French entanglement with dictators such as Habyirimana of Rwanda and Jean-Bedel Bokassa of the Central African Republic was driven by an odious mixture of sentimentality, grandiosity and paranoia. Among Africanists this is called the Fashoda Syndrome, after the collision - literal and metaphorical - of British and French interests in the Sudan during the 19th-century scramble for Africa. Throughout the 1980s and '90s, there existed in the Quai d'Orsay a belief that Anglo-Saxon influence was threatening francophone Africa.

Mitterrand, in particular, sentimentalised about a French family in Africa united by language and looking to Paris as the eternal mémÿre, benevolent and occasionally stern. In return for vast oceans of aid money and the dispatch of troops in times of crisis, the francophone despots humoured the post-imperial fantasies of Giscard and Mitterrand. Here in Britain I am not aware of any mood, even among the most extreme imperial nostalgists, for the insidious recolonisation of Africa that did so much harm to France.

British forces are in West Africa because the overwhelming majority of the people want them there. This is not Vietnam, where Kennedy's pledge to "bear any burden" helped to set his country on the road to agonising humiliation. The British are not facing the dedicated and strict Viet Cong. The Rebel United Front, the West Side Boys, the Kamajor militia and all the rest are doped-up, drunken gunmen. Instead of ideology they have blind rage. Set against the army of Sierra Leone, these militias will easily take control of the country once again. Faced by the likes of the paras or marines, they will eventually melt away.

But in practical terms, I can't see how the current detachment of 200 Royal Irish Rangers is anything like a sufficient deterrent to the desperadoes out in the bush. They will bide their time and rearm. It will take a long time to train an efficient government army. The countryside will have to be won back. We are talking about a period of years, not months. The presence of a British garrison working alongside West African forces (especially those of Nigeria) is the only hope for stability. Those who sneer at the Sierra Leone intervention as an example of "ethical foreign policy" gone disastrously wrong have missed the point entirely. It isn't about policy; it's about honour.

The writer is a BBC special correspondent