Racetracks in Britain

Go Greased Lightning!
For my latest casebook No Matter how Improbable I need Portia to detect that someone has recently been at a racetrack, therefore the morning has been spent learning all about racing in England.
I knew before I started that the Romans loved to race, and with their expansion into Brittania centuries ago, racing might have come with them, but I didn’t know how much modern-day racehorses owed to England.
Did you know that “All modern thoroughbred racehorses can trace a line back to three foundation sires which were imported to Britain in the late 17th/early 18th centuries[3]” ? That is crazy to me. It’s like the stat about Genghis Khan being the progenitor of 0.5 percent of the male population in the world.
Anyway, back to my storyline, I needed a racetrack that existed in 1930, was close enough to London to be traveled to without staying the night and had the potential to have a type of earth/soil that could be distinguishable.

UK Soil Types
I believe Kempton Park Racetrack satisfies these requirements, and at the time, one could take the tube to London Waterloo Station to partake in a day of horse-racing. Kempton is in Sunbury-on-Thames, a town 21km southwest of central London and flanked on its south side by the River Thames. Now to figure out if there is a specific kind of loam or soil I can identify from the area – take a look for example at this map of UK soils from this online forum.
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