The British Transport Commission (Pensions of Employees) Regulations 1953

2.  Where any person, being a pensionable officer or servant, is entitled under his pension scheme, on ceasing to be a pensionable officer or servant, to receive any payment by way of a return of contributions paid by or in respect of him, with or without interest thereon, he may, at any time within three months of the date upon which he loses his employment as a pensionable officer or servant, exercise his right to receive such a payment; and where such a right is exercised by any person the subsequent provisions of these Regulations shall not apply to him, and the persons managing the scheme, the persons in whom any fund held for the purposes of the scheme is vested and the Commission shall be discharged from all other liability under the scheme to or in respect of that person or to any other person by reason of that right having been exercised.