You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
London

Context:
Policing in Greater London, with the exception of the City of London, is provided by the Metropolitan Police Service, overseen by the Mayor through the Mayor's Office for Policing and Crime (MOPAC). The City of London has its own police force – the City of London Police. The British Transport Police are responsible for police services on National Rail, London Underground, Docklands Light Railway and Tramlink services. A fourth police force in London, the Ministry of Defence Police, do not generally become involved with policing the general public.

Question:
What agency is responsible for policing rail services in London?

The British Transport Police