CLRNC CONFUSION AS TO SEQUENCING 3 ACFT ONTO RWY WITH CLRNC TO 'LINE UP AND WAIT' LEADS TO A B777 FLT CREW BLOCKING A B747 AT EGLL; FO.

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CAPT WAS GIVING 'PREPARE FOR TKOF' PA WHEN EGLL TWR SIMULTANEOUSLY GAVE INSTRUCTIONS TO 'LINE UP AND WAIT AFTER ACR Y ON OPPOSITE SIDE OF RWY DEPARTS.' THE CLRNC WAS ACKNOWLEDGED AND CONFIRMED BY THE FO WITH THE RELIEF PLT LISTENING AND CONFIRMING THE INTERP OF THE CLRNC. THE CAPT WAS AWARE OF THE TWR'S CALL AND AFTER FINISHING THE PA AND GETTING BACK ON TWR FREQ WAS GIVEN THE TWR'S INSTRUCTIONS BY THE FO AND RELIEF PLT WITH NO DOUBT AS TO THE INTENTIONS OF WHAT WE WERE TO DO. THERE WAS AN ACR Y B767 OPPOSITE US; AND WHEN HE TOOK OFF; WE PROCEEDED TO 'LINE UP AND WAIT' WHEN IT BECAME APPARENT THAT AN ACR Y B747 WHO WAS #2 BEHIND THE ACR B767 OPPOSITE US WAS ALSO TAXIING TO 'LINE UP AND WAIT' AFTER THE ACR B767 WHICH HAD JUST TAKEN OFF. WE WERE TOLD TO HOLD POS; BUT THERE WAS NOT CLRNC FOR THE B747 TO TAKE OFF IN FRONT OF US. THE TWR ASKED THE ACR Y B747 IF IT WOULD BE OK FOR US TO TAKE OFF FIRST; AND HE SAID THAT WOULD BE ACCEPTABLE. WE WERE CLRED FOR TKOF. THE CAPT HAD NOT HEARD THE TWR'S ORIGINAL CLRNC TO 'LINE UP AND WAIT' BUT THERE WAS A READBACK BY THE FO WHICH WAS CONFIRMED BY THE RELIEF PLT AND NO MENTION OF FOLLOWING A B747 BEHIND THE B767 WHICH WAS IN THE #1 POS OPPOSITE THE RWY. THERE WAS NO DANGER TO ANY ACFT; BUT THERE WAS A MISCOM IN SEQUENCE FOR TKOF. WE HEARD NOTHING FROM THE EGLL TWR AFTER TKOF.