Not only did she have no idea that Peggy (Barbara Windsor) was planning the bash, Jack (Scott Maslen) hasn't actually got round to popping the question.
Feeling humiliated, Ronnie (Samantha Janus) rings Jack demanding an explanation, so he runs straight over to the pub to belatedly propose.
After a good deal of grovelling, his girlfriend accepts and suggests they slip home for a private celebration of their own.
However, Jack is the one who gets a shock when he then catches Ronnie with a condom in one hand - and a safety pin in the other.
Can she convince him it isn't what it looks like, or are the couple about to set a new record for Walford's shortest engagement?