The British Army has always shown that the virtue of nobility is not confined to the officer class. Lieutenant-Colonel Rupert Thorneloe and Trooper Joshua Hammond died the death of heroes, in the service of their country. It would be naive to suppose that any conflict, especially one with such a tenacious enemy as the Taleban, could be conducted without casualties. The sacrifices made by these two young men, and by their many colleagues before them, are the tragic concomitant of a military commitment that, in the view of this newspaper, is in a just cause.

That said, these deaths cannot simply be ascribed to doomed heroism. It is now clear that the Taleban are directly exploiting the weakness of the Viking, the Army’s favoured personnel carrier. Huge roadside bombs, sometimes two placed together, can rip through the weak underbelly of the Viking. When the carrier was first sent to Afghanistan in 2006, its versatility and manoeuvrability made it a great addition to the armoury of the troops. But the increased strength of Taleban bombing exposed a hitherto concealed weakness. The Viking cannot bear sufficient armour to protect its occupants.

Last December, after a great deal of pressure, Gordon Brown agreed to spend £150 million on replacement vehicles, known as Warthogs. But these will not arrive until 2010. In the meantime, our troops will sit in the stifling heat, vulnerable in the knowledge that their defences are not nearly sufficient.

It should have come as no surprise, in a dynamic combat zone, that the enemy has adapted to our technology. It is true that any reinvention of British equipment will take time. A thousand armoured vehicles have been on order since 2006: only 440 have been delivered. But the imminent redundancy of the Viking was predictable. This is one more example of the unacceptable fact that British Forces in Afghanistan have not received adequate funding and support.

The most conspicuous example of this lack of support goes right to the top. In April this year, despite the pleas from the Defence Secretary, from military chiefs and from commanders on the ground, the Prime Minister refused to commit 2,000 more troops to the region. The American surge, which should have been a reason to send more troops to support our ally, was instead used as an excuse to avoid the costs.

The state of the public finances is parlous, of course. There has been a less than enlightening argument about which of health or education should be protected from the cuts to spending that everyone except Mr Brown accepts are inevitable. The defence budget has not been mentioned. It is obvious where the Prime Minister’s priorities lie and it is hard not to think that those priorities reflect not just his calculation of political advantage but also his sympathies.

There are some tough decisions to come on spending. But the defence equation is clear. Either this country desists in considering itself a major player in world events or it commits itself to the cost of engagement. Five men have been Defence Secretary since 1997 and none of them has been especially successful in his negotiations with the Treasury.

The decade-long dispute between Tony Blair and Mr Brown was debilitating to good government, regardless of the department into which it spilt over. But perhaps nowhere was it more important, because nowhere are the consequences so material, than at the Ministry of Defence. It is invidious to say that any particular tragedy is directly the product of miserly funding. In war, death has so many doors to let out life. But we cannot let noble men and women go into battle in vehicles that are patently inadequate for the task. Their nobility demands more of us than that.