Set visitors on twitter already have reported it and now we have an official note by
dover-express: The Age Of Ultron-crew is continuing shooting at Kent, specifically the Dover Castle at the moment. No specifics are available yet, but set visitors claim to have spotted not only Robert Downey Jr (confirmed) but also Samuel L Jackson and (supposedly) Scarlett Johansson. The actors again have been brought in with a private helicopter.
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An English Heritage spokesman said: “Due to a private special event, the second floor and roof of the Great Tower at Dover Castle is inaccessible between June 9 and June 24.
“Visitors are able to experience the ground floor and first floor of the Great Tower and the rest of the 80 acre site including the Secret Wartime Tunnels as usual.
“However between June 16 and 18, the whole of the Great Tower is inaccessible.
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Security is tight but if you're close to the area, maybe you get lucky enough to have a visual.