The postbox at the Delivery Office (opposite Ally Pally station) appears to have been broken into - it's criss-crossed with yellow and black tape, and a woman at the counter said that it was going to be made more secure, and could not be used until the work was finished. BUT they will take letters for posting at the counter during opening hours (8am-12.30pm Mon, Tues, Thurs, Fri, 8am-8pm Weds, 8am-2pm Sat).
I use the postbox there a lot now that most (all?) letterboxes around here have a 'last collection time' of 9 in the morning! The last collection time is still 5.30pm weekdays, and noon on Saturdays, at the Delivery Office.