When the Lord Mayor's procession first moved to the land rather than travelling down the river - where it had given us the word 'float' - the City's dignitaries travelled on horseback.
That lasted until 1711, when Sir Gilbert Heathcote fell and broke his leg on his way to pledge allegiance, and the Lord Mayor hasn't ridden since. A coach and four was hired, such as the one you see in Hogarth's Industry and Idleness, until on 4th April 1757 Sir Charles Asgill commissioned the magnificent State Coach from Joseph Berry of Holborn.
The coach cost £1,065.0s.3d, making it both older and more expensive than the similarly ornate State Coach used for coronations, but the huge cost was nonetheless met by the Aldermen of the day. In modern money that's about £120,000, so theirs was quite a substantial donation to the City, but it has been estimated that just to construct a facsimile today would cost over £2 million. Its real value is incalculable.
In 1777 the coach was taken over by the Court of Common Council. It has been used in every Show since it was built - now 250 years ago! - and between Shows it can be seen in the Museum of London.