The title is a reference to "<<https://bletchleypark.org.uk/wp-content/uploads/record_attachments/1775.pdf|A Bletchley Alphabet>>" which lists some characters working at Bletchley Park, the British codebreaking centre in the second world war. The entry for F describes cryptographer and dance deviser <<ddp:Foss, Hugh#129>> who can regularly be seen "dancing a reel by the lake". When not dancing Foss was in charge of decoding Japanese naval ciphers.

The dance starts with an echo of <<ddd:J. B. Milne#3172>>, contains a reel and then a circle to represent the lake.