What happened
British Rail was privatised in the most complex way imaginable. Rather than selling a single vertically-integrated operator (as happened in other countries), the Major government separated infrastructure (Railtrack) from rolling stock (ROSCOs) from train operation (TOCs). The result was a system with no single entity responsible for end-to-end quality.
Railtrack, the infrastructure company, was run for profit. It cut safety-critical maintenance. Between 1997 and 2002, there were four major rail crashes: Southall (7 dead), Ladbroke Grove (31 dead), Hatfield (4 dead from a cracked rail that engineers had flagged), and Potters Bar (7 dead). After Hatfield, Railtrack was effectively brought back under public control via administration.
The UK now pays among the highest subsidies per passenger-kilometre of any European country — more than if the railway had been kept public. French SNCF, which remained state-owned, consistently outperforms UK operators on punctuality, price, and investment.