I live a double life. I was brought up speaking a language which predates the Roman invasion of Britain. When I’m frightened I swear in ancient Brythonic idioms. Yet I’m a city dweller, and surf the net using the language of the Saxons who pushed the Welsh into the hills of western Britain in the sixth century. I write in both languages. It’s a difficult domestic arrangement, but it holds.

One of my survival tactics until now has been to keep both sides of my linguistic family apart for as long as possible. I publish one book in Welsh, the next in English. Translating my own work from Welsh into English has held little appeal, simply because the audience and concerns addressed are distinct and, often, mutually antagonistic. Also, I dislike repeating myself.

The death of the Welsh language has been predicted for many centuries. With devolution some political optimists declared that the battle for the language had been won. I disagree, having seen my grandparents’ village changing from being virtually monoglot Welsh to being a rural community which will have more in common with the Lake District or the Yorkshire Dales than with its own past in the Cambrian mountains. If the language is dying it seems important to know who or what killed it.

In 1999 I wrote a book-length detective story investigating the murder of my mother tongue, calling it Y Llofrudd Iaith, ‘The Language Murderer’. The plot of the original book was set in a West Wales village, where an old lady, my embodiment of the Welsh language, had been found dead. In the book as a whole I wanted to explore how we could free ourselves of the idea of a “mother tongue” with all its accompanying psychological baggage and its infantilising of native speakers. Detective Carma, half-Welsh, half-Japanese, was the investigating officer and I’m not going to tell you the outcome.

Can you imagine having to speak Spanish for the rest of your life because everybody else around you has stopped speaking English at home? The prospect of losing a whole culture is an existential nightmare for a Welsh-speaker, fraught with questions of one’s own responsibility in preserving collective values without becoming a parrot for the past. To most English speakers, it can’t seem any more important than the loss of Morris dancing. I was persuaded, however, that the fate of a language might be of interest to those concerned with the wider linguistic ecology – after all, if endangered plants offer cures for cancer, what essential directions might be hidden in obscure Welsh proverbs about never ploughing at a run?

The first section of Keeping Mum represents as much of The Language Murderer as I was able to translate in a fairly direct fashion. Only a handful of the poems are literal versions. Richard Poole translated ‘Her End’ in consultation with me. Revisiting the subject stimulated entirely new poems in English, and I allowed those to take shape. These are translations without an original text – perhaps a useful definition of poetry.

Section two of this book is a more radical recasting of my original detective story and a meditation on mental illness and language. In his essay on poetry and psychoanalysis in Promises, Promises, Adam Phillips quotes Lacan echoing Freud: ‘Psychoanalysis should be the science of language inhabited by the subject. From the Freudian point of view man is the subject captured and tortured by language.’ My translated detective was to be a psychiatrist in a mental hospital, investigating how abuses of language had led to his patients’ illnesses.

Therapy’s based on the premise that an accurate description of a situation releases the patient from being neurotically bound to it. Psychoanalysts have even more faith in language than do poets. In the face of experience our explanations always break down. Far from being a failure, however, this wordlessness is usually a clue that something more truthful than our own account of the world is being approached: the ‘keeping mum’ of this book’s title.

The third section of the book, Chaotic Angels, looks at communications between different realms of awareness. Commissioned by Kathryn McDowell, Director of the City of London Festival for the Angel Series of concerts in 2002, the sonnets were written to match Dragan Andjelic’s canvases exhibited in the Wren churches of the City. They focus on angels as messengers from another realm. I use the language of modern Chaos Theory to re-imagine angels as part of our everyday lives – at the centre of experiences like depression and bereavement.

Detective, psychiatrist, angel – the sequence of communicators leads out ever further, in the service of a clarity which is not my own.