Damn Flemings. Invest in something noxious (I gather they are unsettled by the odour of savoury popcorn) which can be piped into their vile catacombs, that'll sort them out, or at least persuade them to up sticks and move down-tunnel to Clevedon (the actual terminus of the Western Extension to the Picadilly Line).

We rousted our infestation of tiny, baritone pirate impersonators using similar tactics and they are now safely terrorising the smaller fauna of Stroud. Good riddance to 'em, say we.