JOHN BLOCKLEY became well-known as an artist in watercolour, pastels and, in later years, acrylic, despite having had no formal training in the subject and not starting to paint full-time until he had reached the age of 52.

Born in Knighton on the border of Shropshire and Wales, Gwilym John Blockley left school at 13 and, at his parents’ insistence, served an engineering apprenticeship. He then had a series of engineering jobs in the North of England before joining the UK Atomic Energy Authority again in a technical capacity, in 1952.

In a remarkable change of tack, and oven by his passion for drawing and painting, he became head of the authority’s design studio. Several of his pictures illustrating atomic power and desalination were displayed in the British Pavilion at Expo 70 in Osaka, one stretching to the full height of the pavilion. His painting of the prototype fast reactor at Dounreay was exhibited at the Royal Academy.

But Blockley was unhappy at UKAEA, and for several years he devoted virtually every weekend to painting outdoors, in all weathers,to capture craggy mountains, bleak moors and industrial subjects. An exhibition of his work in 1965, ridiculed by his boss, astonished both the artist and his critics when virtually everything sold.

Emboldened by this commercial success and, as ever, with the staunch support of his wife, Margaret, Blockley finally took the plunge in 1974, at the age of 52, giving up his well-paid job to paint full-time. He never looked back, devoting his prodigious energy to painting and the obsessive search for the essence of his subjects.

He loved the ruggedness of the Curnbrian and Welsh mountains, the Pennines and the singular mood of the Pembrokeshire landscape. All the time he experirnented with new techniques, developing a style which continued to evolve but remained unmistakably his own: experimental and progressive, with no boundaries; somewhere between abstract and representational, stark but richly patterned.

His talents were not confined to producing distinctive and technically accomplished work. He was also an inspiring teacher, running courses every year from 1967 until illness forced him to retire last summer.

He was elected a member of the Royal Institute of Painters in Watercolours in 1967 and served on its council for many years. But it was at the Pastel Society, an organisation whose aim is to promote the medium by means of exhibitions, tutorial workshops, demonstrations and lectures, that he made the most impact. He joined in 1969 and showed a sense of purpose as its president for two terms (1981-83 and 1988-93) which helped to revive both the medium and the society. He was also a member of the New English Art Club and of the Royal West of England Academy. His energetic leadership, outgoing personality and dry wit made him a popular colleague among artists and students alike.

After retiring from the Atomic Energy Authority he moved to the Cotswolds (though he sometimes complained that the area was "too pretty"), where his wife managed their successful gallery in Stow-on-the-Wold. He shared a studio with the artist Moira Huntly, each benefiting from the other’s criticism.

Blockley also wrote seven books on watercolour and pastel techniques, the last of them appearing last year. Among the most popular was Country Landscapes in Watercolour, in which the artist explained how to achieve a strong textural interpretation of the countryside by mixing watercolours with gouache, Indian ink and other mediums. The text also demonstrates how to handle different terrains, buildings, close-ups, lighting and weather effects. Another popular book was A Personal Record, an illustrated account of a year in his life.