Winston's Walk ("Winston" is John Lennon's middle name) is a short instrumental, written by John Lennon some time in 1960 or before. Whether and to what extent Paul McCartney contributed to the song is unknown.
The Beatles performed this song in their Cavern Club days, probably as a warm-up for performance sets, and it is thought that they also played it in the early days of their touring.
Winston's Walk was never recorded in a studio (so far as anyone knows), and no bootleg has been circulated.
In 1960 the Quarrymen made some low-fi rehearsal tapes, and Winston's Walk is said to be among the songs in that collection, but it has never been released. The song has not been found in other tapes made at the Cavern Club.