Leasehold Home Insurance from Landlord

Disco2002

We have a private detached house under leasehold, and we are still in our mortgage. Our leasehold landlord changed recently and the new landlord is telling us we need to take out their approved home buildings insurance with Zurich through them because they say there is a clause in the lease that says we have to take their insurance, and if we don't they will take legal action.
I've read the lease and it is not so definite as their harassing and intimidatory communications make out, and I thought there had been a change in the law 15 years ago to stop landlords from imposing this type of clause. So long as our Home Insurance is with a reputable insurer and satisfies certain aspects, then I was under the impression that we were free to take out our own Home Insurance policies.
The previous landlord who sold the lease on had never tried to apply this clause in the 20+ years we were paying our Groundrent to them.

Sandtree

I own a leasehold house and my lease requires me to arrange insurance with an insurer nominated or appointed by the landlord. Can I choose my own insurer? - The Leasehold Advisory Service (lease-advice.org)