Why don't trains in Great Britain use eddy current brakes?

[Taunton]

Read it described that descending hills in London, such as at Highgate, or Dog Kennel Hill in Dulwich, was a bit tedious, as the car would roll with gravity up to a certain speed, then apply the mag brake to reduce this somewhat, roll again, mag brake again, all the way down. It seems it was either on or off. I believe it was a Westinghouse product.