The Lord Mayor's Show is the largest unrehearsed procession in the world. Three and a half miles of people, horses, vehicles, soldiers, bands, bicycles, tanks, open fires, ancient carriages and giant fish have to be assembled early in the morning, marched to Aldwych, hidden away, lunched, reassembled in the right order, marched back to the City and eventually dispersed.

Meanwhile the streets have been inspected, the construction works approved, the manhole covers lifted and sealed again, the marshals and police briefed, the participants organised and the State Coach brought very carefully round to the Guildhall. The new Lord Mayor has been rehearsed, television cameras arranged, finances held together and the roads of the City covered in sand for the comfort of the horses. The flypast will fly past, the horses will not be spooked by balloons and breakfast will be served very, very early to the 150 marshals of the Show.

People are often surprised to see that the timetable for the Show is calculated to the second but the procession would be impossible without that kind of accuracy and attention to detail. A delay of a few seconds opens a gap ahead and causes more delays behind. Gaps and delays are not allowed.

The person who prepares all this and makes it work on the day is Dominic Reid OBEarchitect, soldier and for over 25 years, the Pageantmaster of the Lord Mayor's Show.

When you see the Pageantmaster he will either be on a horse or standing in the back of a ceremonial Land Rover wearing the remarkable hat that his daughter has likened to a roosting chicken. He will look calm and perhaps a bit relieved, giving no sign that he was up at 4am inspecting the route or that he has worked for nine months to make the Show look as though it requires no effort at all.