What should I do if I have accepted an offer of a training contract from a small commercial firm and I have now been invited for an interview at a large City law firm (which I would prefer)?

In my position, I can only advise you in accordance with the Voluntary Code of Good Practice in the Recruitment of Trainee Solicitors, which is available on the Law Societys website. Under the Code, students responsibilities include the following: Once a student has accepted an offer, the student must inform all other employers who have made an offer inviting them for interview and make no further applications for a training contract.