Threlfall is portraying the bard of the Lakes in a BBC series, to be screened later this month, which will examine the influence of the Romantic poets and their effect on modern thinking.
The BBC2 programmes, created by the writer Peter Ackroyd, are among a number of events that will celebrate the Romantic era during the coming months. It includes an exhibition of works at Tate Britain, which opens in February.
Threlfall, 52, is renowned for his versatility, having recently played the Duke of Edinburgh in Channel 4's The Queen's Sister. He is currently starring in the third series of Shameless as tragic, booze-sodden Frank.
He said: "It's the variety that interests me. You know what it's like - you get bored talking to the same people all the time. I suppose all it is is dressing up and pretending to be different people really, but it gives me a great deal of pleasure."
Threlfall, who filmed in the Lake District, West Country, Paris and the Alps as he followed in Wordsworth's footsteps, said: "I'd always thought of him as a rather prissy poet who wrote about daffodils. I did have a copy of his complete works sitting on a shelf and when I started going through it I realised there was a lot more ground covered.
"There were a lot more of the common feelings of everyday folk - 'The Shepherd', 'The Idiot Boy', as well as 'Tintern Abbey'. What was fascinating about filming this was to be reciting the words of Wordsworth in the places that they were written."
Ackroyd's series looks at a range of poets and philosophers from the Romantic movement, examining their revolutionary effect in transforming European thought in the late 18th and early 19th centuries, edging aside the absolute power of the church and monarchy, to put the desire of the individual centre stage. Among the figures covered are Keats, Coleridge, Blake and Shelley, with Doctor Who star David Tennant playing Rousseau.
Ackroyd began reading the Romantics as a schoolboy and they have played a part in his life ever since. Nevertheless, he found working on the series opened his eyes further to their importance.
"I came to see the Romantics as more committed to the problems of the day, and part of the revolutionary period of the time, than I had previously realised."
The visual impact of the period will be explored in Tate Britain's major new exhibition Gothic Nightmares: Fuseli, Blake and the Romantic Imagination which opens on 15 February. Later this year the British Library will make one of Blake's manuscripts available for the first time. The notes have been out of the public domain because the pages are toxic, but it has been digitised and will be available page by page online. It contains a draft of the poem "The Tyger" and important sketches.Reuse content