I think it is a "secret" work by Christo and Jeanne - Claude.

 

Christo Vladimirov Javacheff and Jeanne-Claude were a married couple who created environmental works of art.

Click to see some of their work. 

Their works include the wrapping of the  Reichstag  in Berlin and the  Pont Neuf bridge in Paris, the 24-mile (39 km)-long artwork called  Running Fence in  California, and The Gates in New York's Central Park

 This "Wrapping" is immediately next door to the carefully restored 16th /17th century Merchant's House, between the City Centre and the historic Barbican quarter.