Armed police have responded to a significant incident at Heathrow Airport, prompting a lockdown of the area. Drivers have been instructed to remain in their vehicles as the situation unfolds. The tunnels leading to Heathrow are currently closed, and both the London Underground and Elizabeth Lines have been suspended. This has resulted in considerable disruption for passengers trying to access the airport. Bus drivers trapped inside the airport have been advised not to leave their buses under any circumstances. The affected bus routes include 105, 111, 278, 285, SL9, A10, SL7, and U3. Emergency services, including police, a firearms unit, ambulances, and fire engines, are present at Terminal 3. The entrance to the short-stay car park has been cordoned off, leading to a significant backlog of vehicles unable to exit or enter the drop-off zone. Rail services to and from Heathrow are also facing disruptions, with National Rail indicating that delays are expected to last until at least 11:45 am. Many rail users have taken to social media to express their confusion regarding the cancellations. As the situation develops, authorities are urging the public to remain calm and follow instructions from emergency services. Further updates will be provided as more information becomes available.