Its performance is unbelievable. A few years ago, I was refuelling a pair of EFs. When cleared to leave, the first guy asked for the block FL450-510 or thereabouts, dropped back, plugged in the heaters, came past, pitched to what looked like about an 80 deg climb and a few seconds later reported entering the block. No 2 then left and requested FL480 and was told "Not above FL450 until cleared, one similar type already established in the block FL450-510.....
When would such a call last have been made to an RAF aircraft, I wonder?