The devices, which enable Taliban fighters to detonate roadside bombs by remote control, are either sent to sympathizers in the region, or carried by volunteers who fly to Pakistan and then make their way across the border.

Details of how British electronic components have been found in roadside bombs were given to David Miliband, the Foreign Secretary, when he visited British troops at their military compound at Lashkagar, in Helmand province, earlier this week…

When asked how the components had reached Afghanistan, the officer explained that they had either been sent from Britain, or physically brought to Afghanistan by British Muslims who had flown over.