Point of order: something that hasn’t already been accessioned into a collection can’t be de-accessioned. This is a very specific Museum term and, particularly in regards to Nationals, has some very strict processes for onward disposal of the item being deaccessioned.
Dedesignated is more likely, especially where another has been designated in its place. However, even this is not a simple process, and is also not directly related to the NRM - dedesignation would not occur simply because the NRM cannot afford something. Plenty of designated railway artefacts are outwith the care of the NRM.
Indeed, in the most recent list published in June 2021 by the Railway Heritage Designation Advisory Board (RHDAB) (formerly the Railway Heritage Committee), there is no reference at all to a complete 313 unit:
https://www.sciencemuseumgroup.org....2021/06/RHC-Designated-Items-Publish-2021.pdf. Indeed I don’t personally recall ever seeing a 313 on the list.
Where much of the reference to a 313 transferring to the NRM comes from is the 2019 Vehicle Strategy document (
https://www.sciencemuseumgroup.org....19/03/op-rail-vehicle-strategy-2019_FINAL.pdf), which listed a 313 as a future aspiration for operation at SMG (Science Museum Group) sites. Whilst some other vehicles listed are designated (and accessioned), not all are - so no precedent is set for the inclusion of any 313.
Whether this remains the case is of course clearly currently up for debate, but in the absence of primary sources (especially where the quoted source is using their terms incorrectly) I would assign it the same status as ‘the man on the platform said’.
