I would not let the Royal Wedding detour my plans. London is always being "Re-tooled". Right now, there is so much construction going on for the upcoming Olympics there. They are replacing much of the antiquated sewer system. Expect road delays, but you could say much of this about most major cities.
Just get yourself a good hotel location, prioritize what you want to do, and make sure you take the weather into consideration.
You will have a great time!
I have been there for other major events and if you steer clear of the wedding venues you should be fine. I was there for the Queens official birthday one year and hardly noticed until a UK colleague pointed out that we should perhaps go and see the procession.
I would certainly consider going and enjoying the ceremonial nature of your time there.
I agree with Stepping Stones and Jerry M.
Much like Pasadena every mid-December with scaffolding going up all along Colorado Boulevard and pre-Tournament of Roses events going on all over town.
These things should not get in your way in either place if you steer clear of pre-event activities related physical preparations.
Besides, London is great in springtime.
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