Emergency lock change (faulty lock) – Is the tenant liable?

I would consider the lock as part of the exterior of the property. As such it is,covered by s11 of the Landlord and Tenant act 1985.

So the burden falls squarely on the landiord. Not aware of any case law on locks specifically. Probably no reasonable landlord would seek to litigate on such a,matter

As the lock was faulty, (of which you have proof), the landlord would be liable for the cost of repair or replacement.
Where you may run into trouble is that your tenancy agreement probably states that you are not to have any work done without the landlord's consent and if you do he isn't liable to repay the cost. (This is obviously so that the landlord can obtain the best quotes). I'm confident however that if your explanation here is accurate that you will be covered.
Firstly, it is something which couldn't wait until the morning. You could have theoretically stayed elsewhere overnight (not reasonable but possible), but your flatmates would have been trapped inside which in a fire would be disastrous. No-one could reasonably argue that this could've waited until morning unless you had another access point such as a backdoor. I presume if you did have another access point you would have used it and not stood outside for an hour or more.
You also tried for an hour to contact your landlord first and weren't able to, so you tried to give him the opportunity to resolve the problem.
Unless he can prove that with a couple of calls you could have had the job done significantly cheaper by someone who was equally available then I would say the landlord is not in a position to argue. Certainly from a moral standpoint.
Send an email with your reasoning. Set it out in a calm and respectful way, so as to appeal to his logical side. Sympathise with the high cost and misfortune that it was a Sunday and he wasn't available when it happened, all just bad luck, but no-one's fault. If you can't get him to see reason then make an appointment with citizens advice centre and they can contact him on your behalf. While they don't have any specific authority, an independent body can have a better outcome when they become involved. People tend to be more detached and reasonable when dealing with an independent body. They are also in a position to advise you on your options should you not be able to reach an agreement with your landlord.

It is your landlord's responsibility. But very pricey, sounds like a chancer, I had exactly the same about 3 years ago and it cost £120. Not sure the destructive open is relevant, how else would they get in?

At the extortionate amount paid for the lock change I am not surprised that the landlord refuses to pay. The tenant obviously though that the landlord would pay and didn't bother exercising caution when being quoted for the job.

Just wondering..... did you get an official receipt for the work done? Also, what method of payment did you use?

Same thing happened to me recently. It cost £60, albeit the work was done during a normal work day and the locksmith didn't rush round. I think in this case the locksmith saw a fantastic opportunity and took it. Although the lock might not be the tenant's problem, the landlord is entitled to expect the tenant would have some sense and question the bill. The only possible way of resolving this is for the landlord to complain to the locksmith and get the bill reduced.

Reply to the comment left by John Clark at 29/03/2023 - 11:45
Normal price for an emergency locksmith.
Landlords responsibility to reimburse the tenants / pay the invoice.

Also check what your tenancy agreement says re keys

As a thought experiment, if you had agreed a silly sum of £100,000 for the lock change without pre authorization would you expect the landlord to pay this after the fact?

I assume you would see in this example that you can't just reach into the landlords pocket and spend what you want.(That's the Governments domain) 🙂

So there's the principle that the landlord must agree to the cost being imposed, as they can legitimately say they are not party to the contract.

But a reasonable landlord would possibly reimburse you reasonable costs. Perhaps getting some quotes for a Sunday lock change would work out how much that is.

I am assuming from the storey the trapped people did not have access to a ground floor window.

Reply to the comment left by Kate Mellor at 29/03/2023 - 10:57
... without consent... with the words 'not be unreasonably withheld' to be implied and treated as a matter of fact by any adjudicator?
Seems at first sight the LL here is unreasonable on the facts?

Reply to the comment left by Judith Wordsworth at 29/03/2023 - 14:59
Well I have never paid anything like that ridiculous amount for an out of hours lock repair. I can only presume that this happened in the London area where people are used to being ripped off.