Emergency alert on Malaysia Airlines flight to London after 'engine trouble' mid-air

A Malaysia Airlines flight to London has turned back to
Kuala Lumpur after reports of 'engine trouble' mid-flight.
The A380 flight bound for London Heathrow had been in
the air for an hour and a half before it ran into trouble.
It was flying at approximately 21,000 ft when engine
trouble struck.
The plane has since landed safely back in Malaysia after
there were reports of 'a strange smell' coming from the
engine.
Fire engines were reportedly called to KUL airport as the
aircraft landed on the runway.