When I have the amp back in my possession I'll try.
<edit/update>
I forwarded the image to the Tech that did the last transformer and it just so happens that he felt bad that his work had failed so he was looking at what he could do. He thought there should at least be a fuse on the HT side that would prevent the transformer cooking again (his transformer was rated 50% higher than the original). He is also going through every component to see what could have generated the fault, there wasn't any obvious cause and the amp operated as per normal when he replaced the original failed transformer).