What is required for Britain to commit troops to Ukraine, and why is US involvement essential?

The British Security Official indicates willingness to commit British forces on the ground in Ukraine alongside other nations, but only if there is a lasting peace agreement in place. However, they emphasize that a US backstop is absolutely necessary for any such arrangement. The official specifically states that a US security guarantee is 'the only way to effectively deter Russia from attacking Ukraine again.' This highlights Britain's view that while European nations might contribute troops, American military backing remains essential for credible deterrence against Russian aggression in the region.