From the very fragmentary information available (mostly general media), it appears the search was initiated as a result of overdue action rather than a Mayday. Also, the description from the French coast guard of 'wreckage' rather than 'the aircraft' suggests the aircraft broke up on impact. The aircraft should have been in radio contact with someone as it was about to cross from the UK to French FIR.
All and all a bit of a mystery until the AAIB do their stuff. However, it would seem like pilot incapacity or spatial disorientation (which seems unlikely given it appeared to be CAVOK at EGMD and LFAT - but may have been a possibilty given the prior post) are two obvious issues that could cause a crash without a radio call or BRS pull.
Last edited by mm_flynn; 22nd Jul 2013 at 09:29.