Keith — Your question is unanswerable. When Walsh formally closed on October 1, 1951, a substantial number of Walsh employees, including a large section of their cutting team, was already working at Tudor Crystal (The Stourbridge Glass Company Ltd.). Here they continued making popular Walsh designs as demand required, with the full knowledge and approval of Walsh directors and management. So, an example of Clyne Farquharson's Leaf pattern with a Tudor mark is not a copy but a perfectly genuine original, made by the same craftsmen but in a different location. Unmarked examples can be difficult to assign to one of the two manufacturing locations, but again are not copies or fakes.
Your piece is not, in my opinion, either Walsh or Tudor. The short stem and the base star are not typical of these two. If you browse through Benson & Hayhurst, you will see that stem only on examples of Webb and Richardson (eventually taken over by Webb).
I've not knowingly seen that mark before. It seems to be an anonymous mark, just stating MADE IN ENGLAND, so may have been a special for one of the big trade buyers who didn't want the manufacturing glassworks identified. Indeed the cut pattern design may not have been the property of a glassworks but of a factor, wholesaler, or a retailer.