There's a thread on the FLYER forums concerning a letter received by the Shuttleworth Collection. It's shown here, but a larger version is available over on the forums.
As you can see, it contains a threat against the aeroplanes in the Collection, and it is a threat that is rightly being taken seriously.
I have no idea if there's a genuine risk to the Collection's aircraft, but it does bring home the fact that in the UK, for the vast majority of the time, aircraft are pretty safe whether they're left outside on strips (fingers crossed), on airfields or in hangars.
Of course, there have been some well-documented criminal acts, like the five substantially damaged aircraft at Redhill in 2003, and latterly there was some damage to aircraft parked outside at Wycombe Air Park just prior to AeroExpo, but to date (and the fingers are still crossed) we've been lucky.
That said... crossing fingers is not really a serious crime-busting strategy, so despite the relative safety we need to remain vigilant, and to encourage other airfield and strip users to join us in aviation's version of Neighbourhood Watch.
I hope the threat to the Shuttleworth Collection is spurious, I hope they catch whoever is sending the letters, and I hope that it isn't, as the police wonder, an 'inside job'.