All part of a cunning, long term plan.
The next step will to get rid of automatic weapons so, those of you under 40, stand by to familiarise yourself with a thing called a Self Loading Rifle, or SLR for short.
Then, ban bullets. It's a proven fact that bullets are a leading cause of death during armed conflict. Hence they should be banned on health and safety grounds alone.
With no bullets, we wont need anything to fire them from so Gordon can have a nice little earner selling all our SLRs, SMGs, GPMGs and SA80s to that nice Mr DinnerJacket in Iran. For some reason the Iranians are buying up all the weapons they can get their hands on so they'll offer Gordon a good price.
Next, reissue all those longbows that have been in storage since 1430 (that's a year, not a time by the way). Might need a bit of restringing but the British Army can turn its hand to anything.
Finally, sit back and relax, contented in the knowledge that you have greatly reduced the death toll in the forthcoming war with Iran. Ignore the fact that nearly all the deaths will be among British soldiers, gunned down by the SLR and GPMG wielding Iranians. Those who point out that the British Army have no arrows for their longbows are clearly racists.