Naturalisation from ILR/Settled: is the UKVCAS appointment necessary?

Due to external circumstances I need to send this application ASAP when I will be able to do so, I have discovered that a biometric appointment may be necessary and I don’t have much time for it.

I never thought about it since I was never requested any biometric before, I did all my statuses on the official app. They may have taken my fingerprints when I got my NiN ages ago but I don’t remember.

Is there any way to know in advance? If I need an appointment what’s the waiting time in London?