Those who think the law as written is potentially a danger to free speech are quite correct, and it’s also worth noting that it mirrors the law in relation to snail mail, originally dating to 1935, where case law has established (my source is the commentary in Halsbury’s Laws of England) that “The test of obscenity is objective and the character of the addressee is immaterial.”
In the wake of the Gay News Trial in the UK, the then editor of The Freethinker, the late great Bill McIlroy, was fined for sending copies of the poem through the post. He was hoping to trigger another blasphemy prosecution at the time, but the authorities sidestepped that embarrassment by using different legislation!
The current law in relation to post, if anyone wants to look it up is ss.85 of the Postal Services Act 2000:
(3) A person commits an offence if he sends by post a postal packet which encloses—
(a) any indecent or obscene print, painting, photograph, lithograph, engraving, cinematograph film or other record of a picture or pictures, book, card or written communication, or
(b) any other indecent or obscene article (whether or not of a similar kind to those mentioned in paragraph (a)).
Similar laws apply to telephone communication.
It’s also worth noting that there is case law in relation to all this, so you have to read the laws in relation to the way cases have been decided.
In relation to “menacing”, that was tested in the successful appeal in Chambers v DPP (the airport bombing joke on Twitter case), where context was found to be important. The judges in that case also said:
Satirical, or iconoclastic, or rude comment, the expression of unpopular or unfashionable opinion about serious or trivial matters, banter or humour, even if distasteful to some or painful to those subjected to it should and no doubt will continue at their customary level, quite undiminished by this legislation. Given the submissions by Mr Cooper, we should perhaps add that for those who have the inclination to use “Twitter” for the purpose, Shakespeare can be quoted unbowdlerised, and with Edgar, at the end of King Lear, they are free to speak not what they ought to say, but what they feel.
Which of course might help you win if you got to trial, but wouldn’t necessarily stop a prosecution in the first place.
“Grossly offensive” was tested in Collins v DPP (2006). According to Halsbury’s:
It is for the justices to determine as a question of fact whether a message is grossly offensive for these purposes, applying the standards of an open and just multi-racial society (ie via the application of reasonably enlightened, but not perfectionist, contemporary standards); and the words must be judged in the context of the message and all relevant circumstances
So whether something is “indecent” or “obscene” is an objective test based on community standards, but whether something is “offensive” can take other aspects into consideration.
Whether a message falls into the category of grossly offensive depends on whether it is couched in terms liable to cause gross offence to those to whom it relates
For an offence to be committed the defendant has to intend his words to be grossly offensive to those to whom they relate, or be aware that they might be taken to be so.
The Collins case, by the way, involved racist language via telephone and telephone answerphone to the office of an MP over 2 years. At the original trial the charges were dismissed, the language found to be offensive but not grossly offensive, and arising from frustration at the way his, Collins’, concerns were being dealt with. The DPP appealed, and won.
The judgment is worth reading.