I ended up as impromptu marshal at the Coldean Lane junction recently. There's one tip for every rider there as they approach the T junction preparing for the left / right.
As they swoop down from Ditchling, all seemed to have it fixed in their heads that "it's all downhill". It isn't.
As they come to the T junction you need to shout at every single one of them "Steep uphill road, change down now !!!"
Before I worked this one out every rider tried to get up this short stretch in something approaching a 90" gear and all failed terribly. One of them nearly ended up under the wheels of a coach as a result.