During the gruelling 17-hour flight between RAF Brize Norton and RAF Mount Pleasant aboard a MOD-charted Boeing 747, the boredom is relieved only by warmed-up meals and even more tepid films fuzzily projected onto screens with 1970s technology.

However, some excellent in-flight entertainment is saved until the final half hour of the flight. Just before descent, a voice from the cockpit invites passengers to look out their windows. There they see a pair of Tornado fighters "formating" on the wingtips.

In these post-9/11 days, the arrival of two fighters packing sidewinder missiles could have passengers frantically texting their final "I-love-you" messages. But the waving pilots are friendly. And anyway, there are those reassuring roundels.

It is not completely clear why the jet jockeys of 1435 Flight (part of 905 Expeditionary Air Wing) go through this ritual every time an airliner approaches the main base at Mount Pleasant.

Some say that they are checking to make sure that no maverick pilots with ill-intent are coasting into the base, hiding in another plane's radar "shadow". Or perhaps the pilots like a change from the daily practice scrambles and mock attacks.

Whatever it is, it is not for fun. On the ground at the sprawling tri-service base 40 miles (64 km) from the capital, Port Stanley, Officer Commanding 1435 Flight, Squadron Leader Pete Brombley, and his colleagues clearly take things very seriously:

"Our job is to deter any incursions in a zone of 150 miles radius," he says very soberly. "We're here to deter. And it's working."

His team works closely with the Rapier anti-aircraft batteries of 16 Regiment RA, which ring Mount Pleasant. Tornado and Rapier crews engage in mock combat daily.

"We are on constant alert here," says a surprisingly blunt speaking Captain Rob Wood of 30 Battery. "Aircraft taking off from the mainland could be here in 40 minutes."

The reason for such blunt speaking is that in nearby Argentina the "Malvinas" cause is still very much alive.

The Argentines have backed out of an agreement to cooperate over oil exploration in the area, and will not allow increased commercial flights between the islands and Chile.

No-one is suggesting that these moves could escalate to conflict. Argentina has made clear it intends to pursue the claim by peaceful means.

But there is always a chance that a rogue element could see the media attention given to the 25th anniversary of the Falklands conflict as a chance for a publicity stunt.

The commander of British Forces South Atlantic Islands, Brigadier Nick Davies, is happy to talk candidly about the situation:

"I would not wish to change what we do here.  I'm here to make sure that we have an efficient force and to make sure that the 1982 conflict does not happen again. And I'm pretty confident I've got the tools."

Those tools are impressive.  As well as Tornadoes and Rapier, there are troop-moving helicopters; a flight of Hercules and VC10 transports and tankers; a destroyer (currently HMS Edinburgh); a Castle class patrol ship; 105mm artillery, and at least a company of infantry with support units.

The Brigadier came to Mount Pleasant from a posting in Afghanistan, and many of his colleagues have also been hardened by the conflicts there and in Iraq.

If such experiences teach anything, it is the need for clear and unambiguous statement of intent and purpose.  That principle was arguably overlooked once in the Falklands.  That seems unlikely to happen again.