Cycling down The Mall

Heya,

I'd like to cycle down The Mall in front of Buckingham Palace.

I know on weekends it's closed to cars, but I've had mixed experiences on whether you can cycle there. On one visit 2 years ago was allowed, on another a couple of months ago I was forced to dismount and cross the road with the pedestrians.

Does anyone know what the latest situation is, and if there's any rhyme or reason to it?