Are RAMS a legal requirement in the UK?
No law uses the term "RAMS" or sets a format for it, but the law does require a suitable and sufficient risk assessment for your work. HSE says method statements are not required by law for most construction activities, although they are widely prepared. The exception is demolition, dismantling and structural alteration, where the arrangements must be recorded in writing before the work begins.
Source: HSE: Construction, managing health and safety (method statements)