Property valuation question

[terminal7]

My son accepted an offer on his flat about 5 weeks ago. He just received a message originating from the buyer's bank claiming that their valuer has been unable to provide a valuation figure for the property due to fire safety risks. My son has been asked to provide either:

a) An original Building Regulations completion certificate for the works or,

b) A Regularisation Certificate?

I have never come across such a requirement. Has anyone come across similar demands?

Thanks

T7

[Gerry557]

Ive not come across this but wonder if it has anything to do with the cladding issue.

[terminal7]

Flat is top half of 1930s brick house converted into flats during 1980s - no cladding.

T7

[SteelCamel]

What works are they asking for the certificate for? The original conversion into flats? That would be out of time for enforcement in most cases, but as I understand it the BCO can enforce indefinitely if it's a safety issue rather than a technical non-compliance. Unfortunately there are a lot of dodgy conversions about so I can understand them wanting to see the paperwork if it looks like there may be an issue.