In The Case of the Lunatic at Large, Mrs Glibb was the mother of Flying Officer John Glibb, who had stolen a Handley Page Halifax with a war load of bombs. Biggles, in trying to locate John, studied his service docket for clues. With almost nothing else to go on, he decided to follow up a slim lead: an entry which showed that John's hobby was wildfowling. Biggles sent Algy to see Mrs Glibb at her Knightsbridge address to ask if she knew where her son used to go wildfowling.
The lead paid off. Mrs Glibb was able to tell Algy that her son had been posted to Aucherlocherbie, a remote bomb experimental depot in Sutherlandshire in the North of Scotland. John had taken a sporting gun there and used to send her ducks and other things he had hunted.