Drifts are the large round-ups organised by the agisters, where ponies are chased into pounds to be checked over. There can be problems when too many people turn up to watch the spectacle of the drift, and get in the way, or divert the ponies, so nowadays the agisters put out warning signs to discourage spectators.
Drifts are quite new. Before the drifts started, commoners would round-up their own animals. ‘Pony catching’ was quite an art!
Here some commoners are heading for a drift near Penn Common.