JSN

It’s all a bit chicken and egg, isn’t it? Whose to say which is the primary / secondary pathogen. To me it seems plausible that the basal decay was there first - held in check by compartmentalisation, supported by a healthy crown, and then Chalara infects the vascular system - weakening / killing off the crown - allowing the basal decay unhindered access to the rest of the stem. It’s highly likely to be a complex web of factors.

Hola - I’m sorry if this sounds a bit harsh, but you really only have yourself to blame here. In that I assume you had some prior contact with the electricity board? At which point you would have had the opportunity to agree a pruning specification and access / timing of the works? Or did they just tip up on a random day and cut to a spec of their choosing? Also - you have already set the pollard and the pruning regime as back to bole every few years so there is little else arb wise that could be done. Finally - from the pics - the trees are a country mile away from the conductors and could easily have been left alone for another three growing seasons before they actually require cutting. I appreciate this isn’t all that sympathetic. Better luck next time they come.