Not to forget the whole point of BT's 21st century network, or whatever they called it, was to get the whole backbone on TCP with hugely upgraded capacity in the expectation of nationwide FTTH. With initially 10, planned 100M connections in every house the backbone needed it. This at a time when half the population hadn't yet discovered dial-up.

Government couldn't see past the old world of cable and watching football, BT pretty clearly could see far past just the TV. It was popping up on the news pretty regularly in the late 80s along with all the interesting things it might bring.

Me, I just wanted to consign my BT Home Highway (128K ISDN) to the bin.

What we ended up with was a travesty with BT restricted to copper only and exchange sharing for ADSL. As someone else pointed out most of what they invented got sold off to S Korea.