Catalogue description British Transport Commission and British Railways Board: Design Panel: Registered Files

There were three file numbering series. The first, until the end of the British Transport Commission, was based on a number/letter/number system in which the first number was the main subject reference number. Some files extended beyond the end of the Commission into the days of the British Railways Board and were renumbered into the next reference system; they are all numbered under their old number with the new number shown in brackets.

The second numbering system is adapted from the British Railways Board Headquarters system, ie number-number-number, the first number being the main subject reference and the second the sub-subject. This system appears to have continued until 1986.

The last system appears to be similar to the second system but all references start with the number 018. As with the first change, files were in use after the second change and were renumbered. These appear under their new numbers with the old number in brackets. The files have been arranged in former file reference order.