The Soviets made indisputably the biggest national contribution to winning the war.Well, it's clear then we lost the war due to the Germans being just the most awesome and best at everything, oh wait.
We were fortunate to be on the same side (up to that point)
Our own most significant contribution was not inconsiderable: but it cannot be measured in terms of forces committed, or casualties sustained, much less by decisive victories over German forces attained by British forces fighting without the support of allies.
It was simply that we did not give in in 1940.
The civilised world should thank us for that alone.
We, on the other hand, should not kid ourselves about our position in the alliance that destroyed Hitler, nor seek to gloss over the manifest ineptitude that prevailed in our interwar military, much less cling to absurd myths about the natural martial superiority of this island race.
You may choose to differ.