From https://www.cyclinguk.org/article/whats-legal-and-whats-not-your-bikeIf I remember correctly, the police were told directly to used discretion and not enforce this.
Fortunately, when FPNs were introduced for pavement cycling in 1999, Home Office Minister Paul Boateng issued guidance saying that: "The introduction of the fixed penalty is not aimed at responsible cyclists who sometimes feel obliged to use the pavement out of fear of traffic and who show consideration to other pavement users when doing so. Chief Police Officers who are responsible for enforcement, acknowledge that many cyclists, particularly children and young people, are afraid to cycle on the road, sensitivity and careful use of police discretion is required".
There is more detail if you follow the link.