Statutory and non-statutory regulations, standards and guidance
The hierarchy
Inspection and testing sits inside a legal framework, and questions test whether you can separate law from standard from guidance.
Statute. The Health and Safety at Work etc. Act 1974 creates the general duty. The Electricity at Work Regulations 1989 are the key set for electrical work: regulation 4(1) requires electrical systems to be constructed and maintained so as to prevent danger, regulation 5 covers strength and capability, regulation 6 adverse environments, and regulation 29 permits work on or near live conductors only in limited circumstances. PUWER 1998 covers your test instruments and probes, MHSWR 1999 requires risk assessment, ESQCR 2002 governs distributors, and Part P of the Building Regulations applies to domestic work in England and Wales.
Non-statutory. BS 7671 (the IET Wiring Regulations), IET Guidance Note 3, the On-Site Guide and HSE guidance HSG85 and GS38 are not law, but a court may treat them as evidence of good practice. Non-compliance does not automatically create liability, and compliance does not automatically discharge the EAWR duty.
Traps. BS 7671 is often described as a legal requirement in distractors - it is not. BS 7671 is also not retrospective: an installation to an earlier edition is not automatically non-compliant. Conversely, EAWR and PUWER apply to every installation regardless of age.
Rule of thumb. A cheap multimeter with long unshrouded probes offends GS38 and PUWER: GS38 expects fused or current-limited leads, finger guards and roughly 4 mm maximum exposed tip.