Sand Martin, Riparia riparia, investigating one of the artificial nesting walls designed for the species at Attenborough Nature Reserve, Nottinghamshire.
@Maguari Do they actually use these holes? There's a similar setup on a reserve near me and I'm told they don't use it because they like to excavate their own holes.
They do indeed - and were coming and going very actively yesterday. There are a few Derbyshire/Nottinghamshire reserves with these and they seem well-used - there's one at Carr Vale in Bolsover that was very busy last year and my local reserve at Avenue Washlands installed a new one last year.
Attenborough is simply the suburb of Nottingham where the reserve is located - with no link, to my knowledge, to any specific illustrious person.