There are 2 parade's, the big one happens friday evening in the city when all the drivers get driven around the town joined by some classics etc,
the one before the race is only along the start straight and normally kicks off around noon, it can be a bit chaotic.
There are also the national anthems where the brits normally put on a good show and the cars line up in 'old LM start formation'.
Most years there is also a support race, this could be anything from classics to very slow single seaters, this normally happens early morning after the pre race warm up at about 9 or 10 am.