The simple answer is that there's no minimum age to travel on a train alone. However, your child should be mature enough to travel by themselves or with their friends. They should also understand the risks and dangers (as well as the benefits!) of travelling by train.

In the UK, there is no specific legal minimum age at which a child can travel alone on public transport, as the law leaves it to the discretion of the parents or guardians. However, individual transport providers have their own strict policies. On Transport for London (TfL) services like the Tube or buses, children are generally permitted to travel alone once they reach primary school age, provided they are deemed capable by their parents, and those aged 5–10 can travel for free with a Zip Oyster photocard. For national rail travel, most train operating companies allow children aged 12 and over to travel unaccompanied without restriction. For children under 12, it is usually expected that they are accompanied by a person aged 16 or over, though some stations may intervene if a very young child appears distressed or lost. The NSPCC suggests that children under 12 are rarely mature enough to handle emergencies or significant delays alone, so while not "illegal" at 10 or 11, it is widely discouraged for long or complex journeys.