Proof of marriage to British citizen

[Cstringer]

Hello,
I have been living and working in the UK continuously since 2004. My PR card/letter shows that I acquired indefinite leave to remain in 2009.

On the basis of this, I applied for citizenship via the residency route. I also provided payslips for the last 6 years. I did this through the nationality checking service.

Now I got a letter from the home office asking me to send my spouse's British passport and our marriage certificate, otherwise they will refuse the application. Am I missing something? Is this necessary, if I meet the residence requirements?

I can send the documents they want but I think they have made a mistake in requiring them, which leads to unnecessary delays. We also need his passport back soon.

Anyone had a similar experience?
Many thanks

[CR001]

Did you put in the form applying under 6(1) of the nationality act or section 6(2)?

[Cstringer]

Section 6 (1). This is why I'm puzzled.