The frenzy of work essentially constructing a gigantic sand pit will be concentrated during the day - as nearby neighbours including the official residence of the Prime Minister in Downing Street won't want to be disturbed.

But preparations for that site in the heart of London and the controversial Greenwich Park site for equestrian have already begun. Underneath both the 20,000 tonnes of sand at the beach volleyball and the massive showjumping and dressage arena will be huge metal decks, currently being manufactured in Preston.

The decks are to ensure a flat surface, particularly important at the 20,000 seat Greenwich arena which has a significant fall line of about three metres. ''To construct a 15,000 seat venue usually involves a year to 18 months planning and to construct it normally takes a year to 18 months but for these Olympic venues the preparation is the same, but the construction is much, much quicker,'' said Drivers Jonas Deloitte project team manager Stephen Jepson.

''Horse Guards is six weeks to get on site after the Trooping the Colour is complete and Greenwich Park is a bit more time, but the aim is to make sure we take as little of the park for as small a time as public so the stadium goes up and then the site is expanded out.''Jepson said constructing the venues with seating and toilets and other paraphenalia is business as usual, but it is the field of play at both venues that adds to the complexity.

The metal deck underneath the equestrian arena has been tested by both showjumpers and dressage riders at Berkshire and found to be acceptable, alleviating earlier concerns it may reverberate and scare the horses with any unusual sensation or noise. When installed the metal decking will be covered with layers of synthetic mix of track.

''The spring and bounce has to be exactly like it is on the ground,'' Jepson said. The same project team will also construct the temporary venues at the Mall for the start and finish of the marathon and road cycling and Hyde Park for the triathlon finish and marathon swimming events.