Fortunately or unfortunately, I'm not sure which, the over-the-back-wall neighbours were out. And the side gate to their garden was locked so I had to stand peering over the wall and calling George. (I should explain: their garden is on a higher level than ours.)
I lured him back - eventually - with a banana.
'Come on, George. Look, mummy's got a banana, yum yum. Mmm, I'm peeling it. Listen. Mm, can you smell it? Yum yum.'
I do hope no-one was listening. It's hard to be calm-assertive when you're trying to make a banana sound alluring.