TWO engine failures.
There were no engine failures. The plane was in for maintenance earlier.
The engine cowlings were not latched properly. The left one blew off early, and ATC informed the crew. Passengers began to film the left engine with the missing cowl.
As the plane was returning to Heathrow, the right engine cowling also blew off, damaging a fuel or oil line, and denting the wing leading edge.
The leaking fluid briefly ignited on the hot engine parts, but the fire was minor and did not last long.
The plane successfully landed without any further incident.
The engine cowlings on these type engines are known for being difficult to latch and for being hard to see that they are not latched properly. There have been bulletins on them before.
BA held all their planes with these engines for a while to makes sure the latches were taken care of.