For Beadnell poet Katrina Porteous, who lives within sight of Dunstanburgh Castle, the melancholy ruin has been a poetic obsession for more than 20 years. Over the last year, Katrina has visited Dunstanburgh regularly, recording the sounds of the place - stormy nights in November, kittiwake time in May, bumblebees in the gorse in summer - and writing about it.

When it came to recording her poem for radio, Katrina wanted to draw on voices other than her own. The poem consists of many layers. In both words and recorded sound, we experience the natural changes of bird, animal and plant-life in the ruin over the course of a year. Weaving through this, and sometimes simultaneously, we hear the echoed voices of its past human inhabitants, and still more ancient voices, those of the wind, the sea and the place itself. This part is taken by the children of Seahouses First School.

Katrina's poem, and in particular the children's chant, draws upon mythology associated with the castle from medieval times. According to the legend of the Seeker, a knight visiting Dunstanburgh finds a girl trapped in the rock and, given the choice between a bugle and a sword to free her, chooses the bugle. The Seeker is then doomed to search for her forever. This story had strong political overtones at the time: during the reign of Henry VI, the king's failure to wield political power (the sword) led to a breakdown of law and order which resulted in civil war. The myth continues to have resonance today. "The children responded to the idea that a myth can be more than just a fairy-story," says Katrina; "that it can be about choices that we all have to make in our own lives".

All through her poem Katrina uses the sounds she recorded to trigger evocations and descriptions of historical incidents, moving backwards and forwards through the castle's 700 year life. So, for instance, in the dramatisation of a raid by the Scots, instead of the noises of battle, Katrina's verse incorporates the sounds of the stormy sea and wind battering the ramparts. Katrina and actor Trevor Fox recorded their parts of the poem on location at the castle in January.

Katrina, who holds an Arts Foundation Fellowship in poetry, is already acclaimed for her work for national radio. She uses the medium to the full, using chants, songs, dialect, antiphony and the layering of language. In her words, the children's voices and the natural sounds, the intimate history of Dunstanburgh - its secret life - is revealed.

Dunstanburgh Castle: a secret as old as the stones
By Katrina Porteous
Performed by Katrina Porteous, Trevor Fox and the children of Class 4, Seahouses First School
Producer Julian May
BBC Radio 4 (92-95 FM; 198 LW), Monday 9 February, 8.30pm