As happened wth David Tennant's Hamlet, it's very difficult to buy tickets today to see David Tennant and Catherine Tate in Much Ado About Nothing at the Wyndham Theatre in London as the website (link here) keeps crashing due to the volume!
Also the telephone lines are constantly engagaeed and people are complaining that they are holding on for ten or fifteen minutes and then they get cut off.
If you are in London the best advice is to go to the theatre as the queue there isn't very long and seats for almost all the performances are still available.
The run is from Monday 16th May until Saturday 3rd September and Press Night appears to be 1st June.
The theatre told us that they only heard last night that tickets were going on sale today which is why they had not arranged for extra staff to be working.
Good luck and remember that all the time you can't buy tickets, other people can't either!