To be honest I don’t really know. The first lot came when Sizewell B opened as the line was extended further to a new substation and the DT’s were turned into D10’s, then followed by L6M D30’s and then L12 DT’s. At this point the line was modified so the D2’s has their double insulator bundles replaced and the quad bundles on the deviation towers replaced into double bundles, yet still carry a quad line. My only guess is that the towers from this line leading into Bramford were replaced as well. I then visited the substation in 2011 and major work was going on there. A BB L6 D60 was being replaced by an L12 DT acting as a D90 and the EVE L6 DT was also replaced with an L12 DT. Then the BICC L6 line got the treatment and the DT for that line was replaced too as an L12. I remember looking down the A14 towards the substation after the work was done and thinking the substation looked different, and I was right! So when the substation was first built it had 6 L6 DTs. 3 BB, 2 BICC and one EVE. Now there’s only 2 left. 1 BICC and 1 BB. The BICC DT oddly feeds an L4M DT which then becomes a PL16 line. I have a photo of the new L12 DT/D90 being strung somewhere, I’ll find it and share it.