British Airways Boeing 787-9 G-ZBKF operating BA143 London Heathrow – Delhi was approaching Liege at 35,000 ft early this afternoon when it initiated an emergency descent to 10,000 ft with oxygen masks deployed due to a loss of cabin pressure. The aircraft turned back to London Heathrow close to Bitburg and returned at 10,000 ft for a safe landing. The aircraft then went into the London Heathrow maintenance facility.