Mr D has been plagued for over a month with the incessant bleeping of a smoke alarm running out of battery and it was even driving his daughter mad when she heard it via their regular phone calls. We made quick work of identifying which of the 5 units was causing the noise (having first tested a different alarm and finding that it had plenty of juice to emit a loud blast) and Leo climbed the ladder to establish how to dismantle it. A quick click with a flathead and he had the top removed, passing it down to me for battery replacement and then it was slotted back into place. It gave a couple more bleeps for good measure and then fell silent. Mr D was delighted he wouldn't have to hear any more bleeps...at least until the next one runs out of battery.