There has been a digger parked on the grass on the far side of Delta now for a few weeks.
The extension to taxiway Bravo was completed by a company called Ryebridge which does a lot of work for the airport. Now that work is finished they have moved on to the short and mid term car parks. The work to the short term is connected with building the new temporary drop off zone and road layout while the work to the mid term is connected with changing the road layout due to the dart.
I am assuming when that work is finished they will start on Foxtrot but Foxtrot is not meant to be finished until 2020. Also with the state of the ground soil conditions will be better when it has dried out a little.