The idea was that Mercury (later Cable & Wireless) would compete with BT ensuring that the market found the best approach to getting cable into the ground and giving the best possible service.
What ended up happening is we now have two or more duplicate networks in most built up parts of the country which are all substandard, because the aim is simply to be a bit better than the other one rather than look strategically to the future, and rural areas that aren’t financially viable are left with the bare minimum service.
It’s a bizarre way to think about nationally important infrastructure IMO.