Meetings were arranged in Whitehall between military officers and Ministry of Defence officials.
Satellite phones fitted with encryption devices were assembled, and the destroyer HMS Glasgow was quietly diverted from training exercises in the South China Sea. Within three days a team of British officers was in Australia.
The military operation in East Timor, which was given official sanction in the United Nations Security Council early yesterday, is a nerve-racking test for several international institutions.
Principally, it is a challenge to the credibility of the UN, in putting into practice the results of last month's overwhelming vote for independence. More pressingly, it will require a big humanitarian operation which will have to feed, shelter and protect hundreds of thousands of homeless East Timorese.
But it is also a military challenge for the new security arrangements which have come into effect since the end of the Cold War.
For the British military establishment the unit being tested is the mysterious Joint Force Headquarters. In military jargon they are known as JFHQ, the 200-strong "deployable element" of Permanent Joint HQ, Northwood. Unofficially, they are trouble-shooters, one of the newest and most ambitious ideas within the British military.
The JFHQ was quietly born in 1998, and the easiest way of conveying the kind of work it does is to list the places it has been before East Timor: Indonesia, Sierra Leone, Albania and the Democratic Republic of Congo - low-level conflicts in some of the most lawless countries in the world.
In May last year a small contingent discreetly made its way to Jakarta, where demonstrations and riots were about to bring down President Suharto. This year it turned up in Sierra Leone after embassies had been evacuated during the civil war.
"Expeditionary operations over strategic distances" is the phrase soldiers use to describe its role: the JFHQ might advise on the security of British embassies, lay plans for the evacuation of expatriates or, as in Sierra Leone, meet and talk to warring leaders in situations regarded as too dangerous for civilian diplomats.
Its staff at the headquarters in Northwood are drawn from all the armed services. Its East Timor operation, gathering this week in Darwin, will be its biggest so far.
The Glasgow docked here yesterday; tomorrow 220 Gurkhas, the core of the British contribution, will arrive from Brunei to be flown on to Dili in four British planes. The British contingent, expected to be under the command of Brigadier David Richards, will add up to no more than a fraction of the 5,000 to 10,000 troops which may eventually be deployed, led and dominated by Australia. But British military officials point proudly to the fact that they arrived in Australia before any other supporting nation.
They draw attention to the usefulness of the Gurkha troops - Asian soldiers under European command - in allaying Indonesian suspicion of a force dominated by white neo-colonialists.
All week the Gurkhas have been enthusiastically offering planning advice to their Australian commanders.
If their mission is a success, quite apart from the relief to East Timor, it will vindicate a new strand in British defence thinking.
Since the end of the Cold War the armed services have faced questions about their role and its expense. Since the handover of Hong Kong in 1997, that question has become particularly pressing in the part of the world described as "east of Suez". Senior officers have always argued that, despite the ebbing of the Soviet threat, Asia is a region of great uncertainty in which Britain must remain capable of playing a military role.
THE PEACE-KEEPING CONTINGENT
Of a total of 8,000 troops the largest contingents will be from
Australia up to 4,500
Canada Up To 600
Portugal Up To 1,000
New Zealand offered 500
France offered 500
South Korea offered 500 Troops
Britain 250-300 Gurkhas
United States c500
Other countries to offer: Argentina, Bangladesh, Brazil, Fiji , Pakistan Sweden China (civilian police).