Green Flash,
Sorry I don't have the pics' - they were all in our photo' files, so supposedly went to Hendon/ IWM, though I have a nasty feeling they and a lot of other files are in someone I 'know's' garage...
Can promise it did happen though, having seen the photo's - it was an early GR1 or quite possibly P1127, can't remember the photo's that clearly -couldn't help wondering what the RR chap ( name & emotions unrecorded ) felt as he bounded across the grass...
As it was before my day I don't know if the pen doors were fitted, presume they weren't or would have been closed; possibly better to let it roam !
Later, in my day I photographed what seemed the largest mobile crane in the world doing stress testing via load cells when the pen was routinely refurbished, the lesson had been truly learned & the chains used would have held a battleship.