I had not taken enough note of the fact that she was walking firmly ahead of me at the very end of the lead, with ears in 'don't talk to me' configuration.
She wanted to go into a field we sometimes use, so I let her in, and since that field is very nearly secure apart from a bit of a gap under the top gate, I let her off the lead to sniff for bunnies and wandered up to the top to stand by the slightly dodgy gate.
After a while she seemed to get bored and went to stand by the bottom gate, so I wandered back down, at which point she changed direction, charged up to the top gate and shot under it, leaving me to stagger back up the hill after her, unable to shout due to sore throat, and set off in achey cold-ridden pursuit.
Fortunately she only went through the hedge into the other field we often use (that field is secure in the summer, when the nettles are tall, because she doesn't like nettles, but they've died down now). She then did the Saluki Prance and led me all around the fields, never looking at me, but always somehow at least ten paces ahead... Grrr. Still, she did get tired of it eventually and came to me to complain that her feet were wet with dew. THAT IS NOT MY FAULT, ROSIE ROO.