On 15/12/1944 UK new Ministry of Civil Aviation ordered 79 Avro 689 Tudor II for the Kangaroo Route - (to be) BOAC, Qantas, S.African A/W - with the intent for a Mark II with Theseus. No Canucks as Canadian Vickers (since 1927 wholly independent of UK Vickers) took a licence to enhance DC-4 with (to be DC-6-derived) pressurisation and Merlin; Co. nationalised 11/11/44; 10% ownership/from 19/9/46 agreement, on 25/1/47 purchase of a controlling stake by (US) Electric Boat Co. C-4M first flight 15/7/46, orders assigned by Can.Govt. for RCAF and TCA; private CPAL chose to join in, despite surplus C-54s. On the same day as C-4M f/f, US passed the (US/UK) Financial & Trade Agreement (Reconstruction Loan) - the one UK extinguished in May,2006. Canada supplemented that with C$0.6Bn.
RR was giving its mind to turbines, not to inserting longevity in Merlin: Hives' attention was secured by threat of DC-6's R-2800 (flew in XC-112A, 15/2/46; later fitted to one C-5), and he chose to retain (to be) 70 ship-sets of business by committing to cost guarantees that (Pugh/Magic of a Name: ) later bit him on the leg. It had been so much easier just to ship 32,377 from Derby, 26,065/Crewe, 23,647/Glasgow. On 11/4/47 he lost all BOAC business on any Tudor (Oz and SA long since gone). On 14/4/47 TCA put C-4M Transatlantic; on 19/3/47 BOAC was obliged to "order" 25 HP.81 Hermes 4 to keep HP going until the Medium Bomber was resolved (design ITP 19/11/47, to be Victor 1).
RAF, in dismay, had to return its 22 C-54D in March,1946, lumbered with Yorks, then Hastings. EveryBrit knew that piston bomber-variants had no hope v.C-54/C-69. BOAC by strategem and guile acquired some £-L-049 and B.377; on 21/7/48 some of the C$ Reconstruction Loan was applied to an order, early, painlessly filled, for 22 C-4, to be flown joyously, 1949 to 1960! Hermes was with BOAC, painfully, 1950-52 (again briefly, post-Comet 1, in 1954), its routes taken up by C-4M.
So: Q: why did newcomer Canadair/Electric Boat succeed where 1909-origin HP and Avro failed? A: tried harder. HP's cable address was Bomber, London.