In the afternoon I came across Ectemnius again. Another female inspecting potential nest holes in a bee hotel, going in and out of them.
I decided to sit and watch the action, faintly hoping the wasp would start digging a nest. I noticed the characteristic carded silk threads of Amaurobius spiders (top shot), and thought that spiders and digger wasps must come across each other with some frequency as female wasps inspect nesting sites. Then the wasp moved to the log pile under the BBQ and walked in and out amongst the logs. She appeared to have walked onto a silk thread and a false widow spider, Steatoda bipunctata, promptly came out of her refuge. A fight ensued, the wasp trying to bite or sting the spider, the spider spreading silk on the wasp and retreating, and repeating the procedure as the wasp became more and more entangled and buzzed intermitently in her futile attempts to get herself free.
The commotion got an Amaurobius out of her retreat, and at some point both spiders were attacking the wasp, although the Steatoda managed to secure it and, when the wasp stopped fighting, the spider cut free the threads that attached the prey to the log, and pull her to the safety of the retreat.
Early stages of the fight
The Amaurobius' legs are visible behind the abdomen of the wasp in the shot above, while the Steatoda secures the jaws of the wasp with more threads of silk
The wasp front end is now tightly wrapped on silk, now the spider focuses on the rear end
The spider drags the wasp to her retreat