Of course there's no requirement, but it's fun and completely safe in appropriate circumstances.
As for old WorryHard ...
"the R&B is a totally unnecessary risk to anyone in the circuit and as such should be banned absolutely." 
Why not go further and get the CAA to make it illegal?
Don't come to Duxford - you wouldn't enjoy it very much.
The important factors are time and place. A busy circuit when other traffic may be endangered is obviously
not an appropriate time or place, but a total ban is silly.
Flash - I know what you mean.
