When I went last year,  leaving from Luton ,  I flew with El Al,    the customs guys took me aside before flying and interviewed me for over an hour.   
Also took swabs of all my belongings and clothes.  It was a right pain in the arse. 
All because I had a lap top with me that had been in for repair about a month earlier and so I couldn't account for its whereabouts for about 2/3 days.   
Surprising really as I have such an angelic face.