UPDATED 1350hrs
Protestors are back in the carriageway affecting northbound traffic.
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The road is blocked northbound due to a demonstration outside Downing Street.
Routes affected - 3, 11, 12, 24, 87, 88, 159, 453
3, 11, 24, 87, 88, 159, 453 - From Parliament Square at Whitehall, A Bridge Street, L Victoria Embankment, L Northumberland Avenue LOR.
12 - Curtail Parliament Square
15 - Curtail at Aldwych
Diversion Reference D37640