The BBC has a very interesting interview with General Sir David Julian Richards on Operation Palliser, Britain's intervention in Sierra Leone in May 2000:

The brigadier who saved Sierra Leone

BBC, 15 May 2010 12:01 UK

In 2002, Sierra Leone emerged from a decade-long civil war and as Allan Little discovers, much of it was thanks to a little-known British brigadier.

The Paras had been sent to Freetown to simply evacuate foreigners
It was an astonishing thing to witness: the fortunes of a whole country transformed in the space of a few days by a single, decisive intervention.
Eight hundred British paratroopers landed at Freetown airport just as the city was about to slip into the terrifying chaos of a rebel invasion and suddenly, unexpectedly, the shape of Sierra Leone's decade-long civil war was altered.
Or so it seemed to me at the time.

It was, in fact, a little more haphazard than that. And, I've subsequently learned, the British reporters on the ground in West Africa - myself included - seem, unwittingly, to have played a small part in it all.
In the report, Richards notes that he systematically expanded the mission from evacuation of foreign nationals to full-fledged intervention, without initially informing his superiors of the shift:

At that meeting, held within hours of the British landing in Sierra Leone, Richards promised the president that Britain would supply arms and ammunition to the government forces.

British helicopters would be made available to move men and material around the battlefield.

And he, General Richards, would, with a small team of British staff officers, take personal command of the war and seek to end it by defeating the rebel forces. In other words, Richards was committing Britain to taking sides in Sierra Leone's civil war.

However, there was one important difficulty. The general's political bosses in London had sent him to carry out a quick evacuation and then leave.

"So," I asked him 10 years on, "you were promising the president all this before you had the political authority from London to do so?"

"Er, yes," he said, "I'm afraid I was, yes."

War plans

For several days, the political leaders in London stuck with the evacuation narrative, while their man on the ground got on with fighting a war.

"Fortunately," he told me, "the military activities and equipment we needed for an evacuation were remarkably similar to what I needed to push back the rebel forces. So in terms of constructing a tale for London, that was useful."

"So wait a minute," I said, "London was kitting you up for a quick evacuation operation, and you decided to use that kit to intervene in the war?"

"Yes," he said.