Things that go *!?/ in the night

Last night I dozed off to the sound of Stephen Tompkinson, in the slot I've nicknamed a "A Book Past Bedtime"- the 00.30 repeat of Radio 4's Book of the Week, which falls between the midnight news and the shipping forecast. A couple of hours later though, I was roused from my slumbers by some very unfamiliar noises on the overnight feed from World Service.

No, I am not referring to the new WS programme schedule, which begins with the clock change this weekend. Although that does contain some controversial new output, and other programmes just wrapped up in new packaging. For instance, the excellent Mark Coles, with whom I once worked at Radio Sussex, will now be presenting a 'new' rock and culture programme which seems very similar to the old one but has a new title. You're not fooling anyone, BBC.

However, it was not a programme but rather the sudden interruption of one by what sounded like radio telemetry, or other data transmission, on the FM frequency of Radio 4 which caused me to fumble for the off switch after a while. Goodness knows what these sounds were, which even my brother could hear in the other room. Was it some engineers in one of the transmission providers carrying out some tests of a new digital system- maybe the much mooted FM answer to AM's DRM- Digital Radio Mondiale?
This would make sense, given that the BBC is heavily committed to the expansion of digital audio broadcasting, and they are one of the big cheese partners in the DRM consortium currently conducting tests on a number of AM frequencies.

Or was it just possibly an embarrasing transmission failure? If anybody has any information or explanation, I'd be most interested to hear it- just hit the comments button at the bottom of the screen.