What are First Class tickets?
A first class ticket entitles you to travel in first-class accommodation. Some services also offer complimentary catering or other items to first-class ticket holders at no extra charge but the offer may vary at different times of day or at weekends and public holidays, at the discretion of the train company.
If you are sitting (or standing) in first-class accommodation without either a first-class ticket or authorisation from the train operator’s staff, you may be charged the difference in fare between the ticket that you hold and the full first-class Single fare or issued with a penalty fare.
You might be able to upgrade a standard class ticket to first class – check with staff for the relevant conditions and costs.