In Scotland you could be charged with the catch-all offence of breach of the peace. This occurs where the public would be likely to be in fear, alarm, or annoyance, at you baring your breasts depending on the facts and circumstances. Do it on a secluded beach and you'd probably be ok. Do it in most other places and you'd get nicked - unless breast feeding a baby (as opposed to a 40 year old man). What a horrible thought.
The Sexual Offences Act 2003, section 66 says that a person commits an offence if he a) intentionally exposes his genitals in public and b) intends that someone will see them and be caused alarm or distress.
I assume that the previous four separate offences are repealed, thus avoiding the debate on what is and what is not indecent.
quiet right. the breasts are not genitals so the offence under s66 SOA (2003) referred to would not suffice.
it would also be difficult to pursue a outraging public decency (common law offence). so leaving sexual offences alone (being bare chested is not 'sexual' as per the SOA) I would be inclinded to believe that if a police constable saw this happening in the street they would use their powers under the public order act 1986 probabaly s.4a or s.5 causing harassment, alarm or distress. which section they choose to arrest for would depend on the circumstances.