I was curious about when Britain started losing its place as a superpower and when was it first economically and militarily surpassed by other nations. My historical knowledge extends up to the initial rise of the British empire and then there is a gap until after second world war and was never really sure when this took place, what caused it but also how Britain reacted or if they even noticed at the time.
This post might be useful in explaining how the decline occurred: https://www.reddit.com/r/AskHistorians/comments/3dr78k/what_exactly_happened_in_world_war_two_for/
An interesting (if not particularly scholarly) article proposes the events around the Suez Canal in 1956 as the final gasp of a superpower in decline. Bereft of colonies or dominions, and without sufficient power or influence to save an asset that it 'rightfully' owned from being nationalised.