From Doc 4444 PANS-ATM
Note 3.— The objectives of the air traffic control service as
prescribed in Annex 11 do not include prevention of collision
with terrain. The procedures prescribed in this document do
not therefore relieve the pilots of their responsibility to ensure
that any clearance issued by air traffic control units is safe in
this respect, except when an IFR flight is vectored by radar.
See Chapter 8, 8.6.5.2.
8.6.5.2 When vectoring an IFR flight, the radar controller
shall issue clearances such that the prescribed obstacle
clearance will exist at all times until the aircraft reaches the
point where the pilot will resume own navigation. When
necessary, the minimum radar vectoring altitude shall include
a correction for low temperature effect.
There's an interesting twist here. UK controllers, at least in the southern flatland where the base of the TMA everywhere is at least 1000 ft above the highest obstacle anywhere, seem quite happy to issue instructions to route to waypoints that are not on an aircraft's FPL route. That's all fine if the instructions continue to come, but when the radio fails, who is responsible for making sure that the aircraft can safely return from that off-route waypoint to its cleared route?
One can argue that its doesn't matter, as you're not going to hit anything at FL70 around London on a DCT between any two point. But when crews used to this never-mind-the-clearance-just-do-as-we-say mentality go elsewhere, they could be in for a rude shock, just like the AA965 crew that didn't make it to Cali.