Mondeo Mk III

This has probably been asked before, but here goes anyway.
Are LED bulbs road legal in headlights or taillights?
I contacted the AA on this subject. The first response was a lot of technical information, but no straight answer to a simple question. The second response, on repeating the simple question, was even more technical information but again no straight answer to a simple question. At this point I gave up!
Anybody know the legal position?