We have just received this information from National Highways which explains the signs at the top of George Hill:

“We’ll soon be carrying out resurfacing works to the A21 northbound and southbound carriageways between Northbridge Street and Johns Cross roundabout. To undertake the works safely there will be a full closure of the A21 northbound and southbound carriageways between Northbridge Street and Johns Cross roundabout. We’ll carry out this work between 8pm and 6am.   Please note emergency services will have escort access through the works.

A21 northbound and southbound carriageways between Northbridge Street and Johns Cross roundabout: Closed Monday 24 August for four nights   

A21 northbound and southbound carriageways between Northbridge Street and Johns Cross roundabout: Closed Saturday 12 September for 8 nights 

There will be signed diversion in place”.