Ministry of Justice guidance sets out clear expectations in terms of police explaining the implications of accepting a caution.
Ministry of Justice guidance on Simple Cautions for Adult Offenders can be found at: https://www.gov.uk/government/publications/simple-cautions-guidance-for-police-and-prosecutors
Section 3 of the guidance states police officers must ensure the offender understands the implications of accepting a simple caution, and consents to receiving the disposal before it can be administered. The implications which must be explained are set out in paragraphs 62-76 of the guidance. This includes the significance of the admission of guilt and the retention and disclosure of criminal record information for future legal proceedings or criminal record checks. Guidance also states police officers should ensure offenders are given the opportunity to receive free and independent legal advice before accepting a simple caution.
Similar points are made in the Ministry of Justice Guidance for Conditional Cautions for Adult Offenders (also in Section 3 of the guidance) which can be found at: https://www.gov.uk/government/publications/code-of-practice-for-adult-conditional-cautions