I seen from our excellent local paper the Oxford Times that we live at the bottom of a triangular area suitable for fracking. So when Penny spotted this visitor from the shower, stabbing away at a particular spot on the lawn, that's what we imagined he was up to.
A friend round for supper then suggested an alternative theory: that the bird, a Green Wodpecker, was deliberately causing vibrations in the soil which might tempt his prey - maybe worms, although they are far less prevalent than in the clay of Leeds - to see what's going on.
A neighbour - the one who fearlessly hosted a spider on his tummy for a recent post - then solved the conundrum. The bird is 'anting', Hoovering up the little creatures from their underground nest (of which we have many in the garden). As it says on the RSPB website which has a much better photo than mine, Green Woodpeckers' diet consists of 'Ants, ants and more ants.'
The bird's laughing cry, known as a 'yaffle', is part of our lives here, along with Greater Spotted Woodpeckers which eat from our other neighbours' bird nuts as above - sorry for long-range blur. its diet is more like 'Nuts, nuts and more nuts.'