Gents,
I think that I may be guilty of introducing a red herring by mentioning 60 deg of pitch for defining an aerobatic manoeuvre. I have done a bit more digging and actually the worst case is a FAA definition which states 60 deg of bank and 30 deg of pitch (with a few caveats); that is what must have prompted me a use the number 60 but incorrectly. The old military flying regs, JSP318 (happy days!) specified 90 deg of pitch or bank. I cannot find any actual numbers in CAP403 and am not actually aware of anything in the ANO (but if there is I would be interested to know). So let's not get hung up on hard numbers. Being pragmatic, there is no more risk in pulling up into a loop from a low height than there is from performing a wings level pass at the same height and, air display rules permitting, I usually pull up from my flypast minima and am quite content if someone does this during a DA renewal.
One item to consider when viewing the video clip that Pittsextra has linked to is that if you view a loop from directly abeam the aircraft at pull-up then by the time it is in the vertical you will view some of its topside and it may appear that it has rolled towards you. Therefore, from this aspect it may appear to have started rolling before it actually has. I am not saying that Pittsextra's judgement is incorrect or invalid, just that I would not actually put a figure on the pitch attitude based solely on a video from just that single aspect. Although not relevant here there is another visual illusion when viewing a loop head on in that the aircraft will appear to have a reduction in pitch rate when close to the vertical because the apparent length of the aircraft, the rate of change of which gives the visual cue of apparent pitch rate, is a function of sine pitch attitude and therefore even for a constant pitch rate the rate of change of apparent aircraft length is non-linear.