This thread ties in with the other one on the go here in 'Legal Issues' which is referring to a friend & 3rd party. As the OP's issue on that might be hypothetical I don't care to answer it, apart from saying that the ground rules changed in August last year.
The police can no longer issue a Section 7 Temporary Permit at will. If the 8-week S.28 extension elapses without a renewed FAC or SGC, they can now legally insist that firearms/shotguns are lodged with an RFD (6.7 - 6.10 need to be read as a whole).

FIREARMS LICENSING: Statutory Guidance for Chief Officers of Police – 2025 issue
Limited automatic extension of certificates
6.4 The chief officer should normally make a decision on an application for renewal before the expiry of the certificate or registration, provided that the application has been made at least 8 weeks before the date of the expiry of the certificate. In the case of firearms and shotguns, where an application for renewal has been made at least 8 weeks before the date of the expiry of the certificate, and the police have not been able to make a decision on the application by the date of expiry, a limited extension of the certificate automatically comes into effect.
The extension begins from the original expiry date of the certificate for a period of 8 weeks or until the police decide the application, whichever occurs first. This extension period allows the police a further period in which to decide the application. This is a statutory extension provided by section 28B of the Firearms Act 1968 and is intended to provide a safety net for applicants in exceptional circumstances where the police are unable to process and decide a case before the original expiry date of the applicant’s certificate. During this period of extension the applicant will remain entitled to possess, purchase and acquire firearms and ammunition as per the conditions of the original certificate. Chief officers should facilitate this extended entitlement by ensuring that the applicant is provided with a letter or other clear evidence that the certificate benefits from the automatic statutory extension. (A suitable letter is provided on the National Firearms Licensing Management System (or SHOGUN in Scotland)).
6.5 The chief officer must always endeavour to make a timely decision on an application that benefits from the extended 8 week period before expiry of the extension period. A failure to do so will leave the applicant without a lawful basis for the possession of their firearms or shotguns and associated ammunition.
Should such circumstances arise, the police should work with the applicant to make the necessary arrangements for the safe, legal storage of their property until such time as the application is decided, or the police may consider the issue of a temporary permit, issued in accordance with section 7 of the Firearms Act 1968 (see below).
Section 7 police permit
6.6 Section 7 of the Firearms Act 1968 allows chief officers to issue a temporary permit to allow for the lawful possession of a firearm and ammunition in accordance with the terms that are set out in the permit. These permits may be used to allow a certificate holder to continue to possess their firearms and ammunition where their certificate is about to expire and an application for renewal has been received. This can apply to circumstances both where an application has been received more or less than 8 weeks before expiry. These permits should not be used routinely to benefit applicants who do not submit timely renewal applications e.g. less than 8 weeks, unless in exceptional circumstances. Temporary permits should not be issued to those who are uncooperative with the police while consideration is being given to their application.
6.7 The police must be satisfied that the issue of a section 7 police permit does not give rise to any public safety risk, which can normally only be determined after full consideration of their renewal application.
Therefore, section 7 permits issued to provide more time to consider a renewal application should only be on an exceptional basis and where unavoidable.
Police are encouraged prior to issuing the temporary permit to check if there are other options, for example in cases of bereavement of a certificate holder, whether they go to another licence holder or RFD. Where required, temporary permits should be supplied with an end date no longer than is reasonable to cover the expected period of processing and should not be issued if no renewal application has been received.
6.8 Chief officers should also avoid routinely using temporary permits as a means of managing licensing caseloads within their force.
6.9 Chief Officers should ensure that their firearms licensing departments are sufficiently resourced to enable effective processing of applications, to avoid the need to rely routinely on the use of section 7 permits.
6.10 While it is the case that some police forces have made significant use of section 7 permits in the past to help manage certificate renewal backlogs with large numbers of people subject to these permits, this practice must now be avoided as it conflicts with the principle of maintaining efficient and effective licensing arrangements.
6.11 Certificate holders must not be asked to rely on an expired certificate or registration. It is unlawful for them to do so.