https://www.theregister.co.uk/2018/10/29/uks_rail_ticketbooking_systems_crash/

Train companies across the UK are unable to take online ticket bookings due to what has been described as a "national issue" with the country's reservation service.

The outage – which appears to have affected all UK train operating companies (TOCs) today – means that users can't book tickets on websites or on mobile apps.