Manchester-London services are among those affected as disruption is expected until 10:00 BST.
National Rail says the fire alarm in a signalling centre is likely to cause hours of delays.
Campaigners call for Sunday rail services' return amid a two-year row between Northern and staff.
Children born in the autumn or winter months are liable to pay an increased fare after their 16th birthday.
Government figures show a sharp rise in delays and cancellations caused by farm animals on railways.
Botley Road, a main route into Oxford city centre, has been shut to traffic since April 2023.
The government wants a 40% increase by 2040 but businesses are calling for more investment.
A plaque is unveiled in honour of the victims of one of Britain's worst ever train crashes.
Social media sensation Francis Bourgeois is supporting the reopening of Cannington Viaduct.
