I am a tenant in the UK. I live on the first floor (2nd floor in US scheme), there is no fire exit and the flat is big enough for a couple. The latch on my flat's door is the Ingersoll 'Classic' Nightlatch that is the first being described on the maker's website:

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This lock can be double-locked from the outside: that is, once the bolt is already locked because the door shut, a clockwise key turn will push it a little bit more in a fashion that will not change anything, except remove the ability to open it from inside the flat -- even for someone with the key; since the only keyhole is on the outside.

That seems super dangerous to me. Imagine I leave in the morning, and unwittingly mechanically turn the key to double lock it. If there's a fire, what is my girlfriend left inside supposed to do? I can't comprehend the purpose of this, and how it is even safe to install such a lock on the single exit of a flat.

What is the purpose of this double lock mechanism? Is it safe and compliant with fire requirements in the UK? Is there a way for someone trapped inside to break free?

(The website presents this as a 'single dweller' option as opposed to a 'communal door' option that is identical but can't be double locked. Even for a single dweller, my questions remain, since any 'single dweller' would welcome guesses once in a while)

  • 2
    i would think that the use of the lock is illegal
    – jsotola
    Dec 12, 2021 at 19:16
  • Your local fire department will know if it is safe and compliant, that is part of their job, besides breaking in to save someone.
    – crip659
    Dec 12, 2021 at 19:42
  • @SolarMike And that defense didn't work too well for him.. Stay safe.
    – JACK
    Dec 12, 2021 at 19:51
  • 1
    If someone outside, e.g., building superintendent, can effectively lock you inside, that would seem an extreme fire hazard. However, the UK may have a different attitude about what constitutes a fire hazard, e.g., theguardian.com/uk-news/2021/may/07/… Dec 12, 2021 at 22:03
  • 3
    This seems like a "there's gotta be something missing, no way that's how it is" situation. Dec 12, 2021 at 23:37

1 Answer 1


It's a deadlatch, a combined deadbolt and latch. It stops a thief from entering through a window and exiting through your front door with your tv etc...

It's safe double locked only when the house is unoccupied, so don't lock people in.

  • This is the only logical explanation for this type of locking mechanism. However, it makes no logical sense to design a lock that works this way. If I were the thief and found myself "locked in", I'd either break another window where I could get out with the TV, or just get peeved off and break everything in the house before exiting via any handy newly broken window. Of course, if this were the US, and there was a fire and I found myself locked in, I'd then sue the homeowner for endangering me, and a US jury would likely find in my favor. <US needs tort reform>
    – FreeMan
    Dec 13, 2021 at 13:09

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