RCC = Removals Core Casework. The RCC examine cases where there is a possible barrier to removal and request updated information on the applicant/applicants, before a decision is made on whether leave should be granted or there should be an order for removal from the UK.
The information in this link may be helpful:
In particular Section 4:
4.2 Issuing Invitation to Interview Letters: When inviting an asylum applicant to attend an interview, staff must be aware that the ACD.0062 ‘Invite to Asylum Interview’ stock letter has been amended to include the following ‘Requirement to submit photographs’ section: Requirement to submit photographs If you have not already done so, please bring with you four unseperated photographs of yourself and each dependant included on your asylum claim. Each photograph should meet the following requirements: Passport size (approximately 4cm x5cm) Recently taken Full face Light background Have the subject’s name, nationality and date of birth clearly written on the reverse. Failure to submit passport sized photographs of yourself and your dependants may prevent the production of an immigration status document in the possible event of being granted leave in the United Kingdom.