IIRC - the 105s used for the more extreme manoeuvres (esp inverted flight) had the rigging adjusted so that at min collective position, they were actually able to get a small amount of negative pitch.
You can fly a loop without lowering the lever at the top but, as Aucky suggested, it won't be a nice, FW-style circular loop. The Lynx loop does have an element of lowering the lever over the top but not as far as MPOG and definitely not sub-min pitch - IIRC the engine oil system just will not cope well with negative G and the white-metal bearings at the input stage don't like being without lubrication.
Although Dennis lowers the lever at the top, I suspect he retains a smooth aft cyclic pull so as not to unload the head.
The real danger of looping - as one of the previous videos shows - is letting the nose drop in the second half of the manoeuvre, the speed will increase very rapidly and you will eat up your recovery height very, very quickly!
Fortunately, unless you actively push the cyclic forward too much, flapback helps with the recovery.