here the AIM issued by the CFMU:
HIGH LEVEL SECURITY IN UK AIRPORTS
----------------------------------
. UPDATE 5
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.
DUE TO THE ONGOING SECURITY ISSUES EGLL AIRPORT IS CLOSED TO ALL
ARRIVING TFC WIE TILL 1800
.
OPERATORS MUST SYSTEMATICALLY CANCEL ALL PLN, RPL OR FPL FOR
THE FLIGHTS THEY DO NOT INTEND TO OPERATE
.
CFMU OPSD ON BEHALF OF LONDON FMP
2 LH flight (1 fro FRA and 1 from HAM) diverted back to origin.