A series of two and three-day meetings runs through the season - including those at Chester and York and the Classic meetings at Newmarket, Epsom and Doncaster.
There are also longer festivals - Royal Ascot and Glorious Goodwood, both of which are five days.
The cards at all these meetings include both conditions races (where horses carry the same weight subject to certain conditions, such as gender) and handicaps (where horses carry weight according to how they are officially rated).
The conditions races carry more prestige while handicaps are more important in terms of betting.
The Pattern, which was introduced in 1971, forms the backbone of the European racing calendar for non-handicap races and gives the season a structure.
The Pattern is designed to provide good tests for horses at the right stage of their development and it also guarantees top-class racing throughout the season.
Three (primarily domestic races).
Linked to the Pattern are Listed races, which are a level below Group Three in terms of importance.
The Pattern can be altered from season to season to allow for races to upgraded or downgraded where it is deemed appropriate.
For example, in 2003, the Queen Anne Stakes at Royal Ascot has been promoted to a Group One race.
British Group One races in 2003
2,000 Guineas (1m, Newmarket, May)
1,000 Guineas (1m, Newmarket, May)
Lockinge (1m, Newbury, May)
Coronation Cup (1m 4f, Epsom, June)
Oaks (1m 4f, Epsom, June)
Derby (1m 4f, Epsom, June)
St James' Palace (1m, Royal Ascot, June)
Queen Anne (1m, Royal Ascot)
Prince of Wales (1m 2f, Royal Ascot, June)
Gold Cup (2m 4f, Royal Ascot, June)
Coronation Stakes (1m, Royal Ascot, June)
Golden Jubilee (6f, Royal Ascot, June)
Eclipse (1m 2f, Sandown, July)
July Cup (6f, Newmarket, July)
KG VI & QE Diamond Stakes (1m 4f, Ascot, July)
Sussex Stakes(1m, Goodwood, August)
Nassau (1m, Goodwood, August)
International (1m 2f, York, August)
Yorkshire Oaks (1m 4f, York, August)
Nunthorpe (5f, York, August)
Sprint Cup (6f, Haydock, September)
St Leger (1m 6f, Doncaster, September)
Fillies' Mile (1m, Ascot, September)
Queen Elizabeth II (1m, Ascot, September)
Cheveley Park (6f, Newmarket, September)
Middle Park (6f, Newmarket, September)
Dewhurst (7f, Newmarket, October)
Champion Stakes (1m 2f, Newmarket, October)
Racing Post Trophy (1m, Doncaster, October)