I shall repeat (briefly) another inconsistency in UK airports - the sensitivity of metal detecting arches. I could leave LTN and be fine but returning through IOM (Isle of Man) wearing the identical garments {duly washed by my mother, I promise!] then the alarm would sound. In the days before regular shoes off instructions, at LTN I could stroll through and at IOM I always got a pat down.
After this happened a couple of times, I commented to the IOM staff that their unit must be set to detect a lower level of metal (lacing eyes on the type of boots I habitually wear) and they declared on more than one occasion that, "All metal arches in the UK are set to the same levels. Over the course of ten years I can tell you - No.