OzBomb.
Canadian personnel and plant were part of the "British" contribution to Manhattan. After McMahon Act, 1/8/46 and ejection of aliens from all US AEA activity, PM Mackenzie King saw no need for Canada to spend solo on such things. When, later, a TransPolar Sov. Threat to Canada became evident, geography integrated Canadian, Alaskan and CONUS airspace. It is to the credit of the Canadian electorate that throughout the Cold War - and ongoing today - they stepped up to all aspects of Alliance defence, excepting only nuclear. So, for example, of RAF's 438 loan CL-13/F-86E, Canada paid for 370.
The reason that in January,1947 UK PM Attlee set about, ah, Anglicising Fat Man from such Intellectual Property as could be retrieved from the memories of Penney and Fuchs (yes, him) was that Truman had set a date of VE-Day+2 years for US Army withdrawal from W.Europe. It wasn't that Uncle Joe was already seen as a Threat, but rather that Statesmen judged that "you never can tell" what might lie to the other side of the hill (that's the exact logic of retaining/renewing a Deterrent today, despite no evident Formed-Power Threat. Today we are not flush: Attlee's UK was utterly skint, yet he chose to spend). After Berlin Blockade and founding of NATO he tried very hard to discontinue Blue Danube: he sought “US bombs onto Br.soil, rather than (pestering for data) to hasten (UK work…willing) to subordinate (target) planning to (US-)integration” and haul US-custodial weapons. Pace McMahon, such porterage was offered 10/49 after Joe One/First lightning. But “it was not to be (after Jan,50 arrest of Fuchs in the Blue Danube team. US/UK/Canada talks) returned (to) a deep freezer” K.Harris, Attlee, Weidenfeld,1982, P290; A.J.Pierre, Nuclear Politics, OUP, 1972, P133.
Australia, similarly, has stepped up in full to its Alliance positions (Korea, Vietnam, Malayan Emergency, Konfrontasi, E.Timor, ongoing)...again, like Canada, non-nuclear. The SEATO Charter covered any Sov, later PRC Threat: what would be in it for UK or US to "share" industrial effort to create an OzBomb? No point. UK was glacial enough trying to link Aldermaston, Ampthill and Burghfield with remote Welsh Cardiff. The notion that GAF Canberra was selected in 1949 as a nuke carrier is flat wrong: it was 1952 before UK judged it could try to do small Red Beard, and 28/11/61 before NEAF deployed it in Canberra B.15.
UK "Independence".
Blue Danube was live-dropped 11/10/56 and then slowly deployed through 1957 in 138 Sqdn Valiant/Wittering, from 21/5/57 in 83 Sqdn Vulcan 1/Waddington, from 1/5/58 in 10 Sqdn Victor 1/Honington: by 30/6/58, maybe 20 deployed rounds. MBF:SAC targeting was in harmony from May,57, “highly satisfactory” Wynn's Official History,P275, and was wholly integrated by MoU 3/7/58: 106 V-Craft (74 with Project 'E' weapons) were to address 69 Counter-Value/20 Air Defence and 17 bomber Counter-Force targets. I.Clark, Nuclear Diplomacy & the Special Relationship,OUP,94,P132. 10 Sqdn. was "independent" for 8 weeks, 83 Sqdn. for 58 weeks - if you ignore our, ah, derivation from Fat Man. 138 Sqdn. was never "independent" as US paid "about half" Valiant's procurement bill Wynn,P.55.
US Sec.Def was briefed 18/6/62, cf >1,000 US warheads, UK had 8 “certainly operational” Clark,P393 (net of attrition also eroding USAF; UK had c.100 “available”); rude to France, he decried small nuclear Forces as “dangerous, expensive, prone to obsolescence and lacking in credibility”: UK PM Macmillan,“deeply suspicious of (US)” sought a modicum of solace, but learnt “doubtful our deterrent (could be used) independently (we had no) serious operational plans (to) do so.” R.Lamb,The Macmillan Years, J.Murray, 1995, P303. RAFG/MBF/TBF Project 'E' weapons, like US weapons hung on other NATO platforms, must remain under US custody until released by the President. They could not therefore be operated in dispersal. US connived at Macmillan's political need for chimerical "independence" to avoid the need to put custodials alongside dispersed "Anglicised" Mk.28 Red Snow, in Yellow Sun Mk.2 and Blue Steel. That's why, later, RAF/MR could pop into Sigonella to pick up Lulu, but RN needed WE177A(NDB).