Thanks Rob.
I took an initial shot at my head height, and hurried off so to minimise the disruption to him (which turned out to be an average shot). He saw me and said "it's ok, you can take it", so I went back, set up low & close and took a series of shots properly.
It made me think about if I hadn't received his invitation, I would end up with a suboptimal outcome with my half-hearted attempt...