At the time I had not identified the bee itself. LNHS expert Tristan Bantock has confirmed from my photos that 'it is the very distinctive (Hairy-legged Mining Bee) Dasypoda hirtipes. Nothing else has such long hairs on the scopa. They do nest in aggregations and like fairly loose sandy soil, as does (the Beewolf)Philanthus, but I am surprised they are nesting (together)'.
The Beewolf does, however, specialise in catching Honeybees, so these Hairy-legged Mining Bees are unlikely to be under attack from their neighbours.
According to the Essex Field Club website : 'This mining bee occurs in southern Britain, and whilst still reasonably widespread and locally common on southern coastal dunes, it has declined significantly inland (Falk, 1991a). In Essex most records are from near the Thames. The bee is remarkable for the female's very large pollen brushes on the hind tibia. The species will form nesting aggregations in bare or sparsely vegetated sandy or other friable soils and females collect pollen exclusively from composites (Asteraceae) especially yellow flowered species such as ox-tongues Picris spp. and ragworts Senecio spp.'
Later (on 16th August) I counted the holes - not easy to do accurately without doing the job rather slowly, but my rapid' rough-and-ready-count' of holes with recent excavate (excluding holes flush with the surface which may be last years' holes and/or abandoned this) gave a total of 570 (yes, five hundred and seventy).
Some photos of the site and bees appear below.
For more information about the variety of bees, wasps and ants that can be found in the UK see the Bees, Wasps & Ants Recording Society website:
Hairy-legged Mining Bee and Beewolf colony by Bursted Woods on Erith Rd, Barnehurst, looking towards Bexleyheath. The pale patches in the grass verge are excavated sand around nest hole entrances. Both are uncommon species.
Early in the day a lot of the bees sit with only the front part of their bodies poking out of their nest holes
Lucky shot of an incoming bee
Three-quarter rear view of female showing dense hairs on hind legs, used as 'paddles' to excavate sand from nest holes
Bee 'paddling' backwards to push more sand out of and away from the nest hole