Dr Ian Plummer

http://www.oxfordcroquet.com/laws/6th/11.asp
Oxford Croquet

11. BALL IN THE YARD-LINE AREA

1. BALLS OTHER THAN THE STRIKER'S BALL At the end of each stroke any ball in the yard-line area, other than the striker's ball, becomes a ball in hand.
2. THE STRIKER'S BALL If the striker's ball is in the yard-line area at the end of a stroke it is played from where it lies unless the striker is entitled to take croquet. Only at the end of the last stroke of a turn does the striker's ball in the yard-line area become a ball in hand.