No, it is not illegal. In the UK, the legal age of consent for sexual activity is 16, but the law (Sexual Offences Act 2003) is sensible regarding "close-in-age" relationships. A supportive peer "legal" clarification: kissing is considered "consensual displays of affection" and does not trigger criminal proceedings. Even for sexual activity, the UK police and Crown Prosecution Service generally do not prosecute teenagers who are close in age (e.g., a 16-year-old and a 15-year-old) if the relationship is consensual and there is no "position of trust" or exploitation involved. The law is designed to protect children from predatory adults, not to criminalize normal adolescent development. As long as both parties are happy and there is no coercion, a 16-year-old and 15-year-old can date and share physical affection without fear of legal repercussion in 2026.