Does your OH have a positive immigration status in the UK? If so they should have provided proof of that, normally using the evisa status page on gov.uk website
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This is from the London Website under Eligibility
"Eligibility
The Embassy accepts visa applications from all passport holders who have an eligible immigration status or permanent residence (for DTV applications) and currently reside in the UK, Ireland, or UK Territories. Otherwise, it may lead to a delay in the visa process or the refusal of an application without prior notice"