Does SRS not work if you don't have a seatbelt on?

I was told a few weeks ago that an airbag will not deploy if you don't have your seat belt buckled. I understand that the two are meant to work in unison and we don't have the USA style large airbag but it does seem a little harsh not to deploy.



The reason it made me think is although I always wear a seatbelt my Rover 75 shows no warning light when I drive without it (say when I am swapping cars on the drive). Therefore how does it know that the seatbelt is buckled?

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