I'd go round to his girlfriend's place and tell her I have a secret to tell her but I'll only tell her if she gets into bed with me
Then I'll put an alarm on my phone to ring in a few minutes, so I'll answer it during sex and tell her I've got to go because my house is on fire, I'll come back another time.
Then I'll repeat the process until I run out of houses to imaginary set on fire, before telling her.