This is a history where FDR died fifteen months early and his then-vice-president Henry Wallace succeeded him. This gave Wallace a head start on the power-brokers who had him replaced with Truman in real life and he won the 1944 election. Wallace was relatively trusting of the USSR and in this timeline he allowed Germany to be re-united as a neutral per Stalin's preference. NATO never came to be as Wallace was also pretty peace-oriented (and an alliance was even further out of the question after the isolationist wing of the Republicans won the presidency in 1948).
Left up against the Soviets without the US to back them, the UK broke the bank to develop intercontinental missiles as well as nuclear bombs, using the smaller-scale prototype rocket to do a suborbital manned space launch. This served as propaganda to get France and the Benelux nations interested in sharing the technology in return for paying for some of it.
This was the dark flip-side of that space program: a land-based test of a fission bomb, a second test of a thermonuclear weapon and then a third using the missile to deliver another H-bomb from Malaysia to Peros Banhos in the Chagos Archipelago.
