hi there! i had been to London 3 times over a period of 1 year and had been asked to have the contents of my Kathmandu Kinetic Bag checked out on my last trip at LHR. (had no such problem at Stansted airport). It contained both Ipad3 and Kindle. Funny thing was my sister also had an iPad in her Doc Marten bag and she was through without a problem. Could be because her bag is a 'proper' bag unlike mine which is more of a foldable nylon thingy
We got through the Gare du Nord station (we took Eurostar to Paris) without any issue.