A futile but joyous irony

Maybelle's been lobbying to have maps and street maps in the lending stock at Helminthdale for the best part of a year now. She's just had another row with Mary about it and has been quietly steaming in the work room since then. Enter Mary:

"I'm going to a meeting in Pardendale this afternoon but I'm not sure where the nearest parking is. Do we have a street atlas?"

"There'll be one up in the reference library," replies Maybelle innocently.

"That's no good, I'll need to take it with me."

"What a pity there aren't any lending copies."