Image caption Academic and campaigner Tedi Millward has died aged 89

Prince Charles' Welsh language lecturer Dr Tedi Millward has died at the age of 89.

Dr Millward, who taught at Aberystwyth University, was a nationalist, an academic and campaigner, his daughter said in a tribute.

He was asked to tutor Prince Charles ahead of his investiture as Prince of Wales in 1969.

The lessons featured in an episode of The Crown on Netflix, titled Tywysog Cymru - Welsh for Prince of Wales.

Dr Millward was played by actor Mark Lewis Jones who said the Prince and Dr Millward developed "a respect for each other during this time even though they came from different worlds".

Image copyright Angharad Elen Image caption Mark Lewis Jones and Tedi Millward on the set of The Crown in Aberystwyth

Dr Millward's daughter Llio Millward said in a statement: "I think firstly of my father as a nationalist.

"His passion towards the Welsh language and culture drove every aspect of him, from his personal life, as an academic and as a campaigner.

"He was very unassuming and I had to nag him to write his autobiography.

"But you could see he was, as the Welsh Language Society's former leader Jamie Bevan said in the foreword, one of the quiet giants of our language and our culture."

Image copyright Llio Millward Image caption Tedi Millward with his daughter Llio

Born in Cardiff in June 1930, he became active with Plaid Cymru and Welsh Language Society, Cymdeithas yr Iaith, along with prominent Welsh historian John Davies.

He was elected vice-president of the party in 1966, the same year he stood for the first of two unsuccessful attempts to represent Cardiganshire at Westminster in general elections.

Mr Millward, who continued as a Welsh lecturer at Aberystwyth, went on to serve as Plaid's spokesman on water policy and advocated non-violent direct action against the construction of new reservoirs.

Media playback is unsupported on your device Media caption Episode six of The Crown sees Charles travelling at the request of the Queen to learn Welsh

Aberystwyth University's vice-chancellor, Prof Elizabeth Treasure, said: "Dr Tedi Millward played a hugely influential role in the study of Welsh over many decades, and his legacy will be an abiding one which will continue to inform all those who follow in his footsteps.

"Tedi made a vast contribution both in academia and society at large and he will be remembered so fondly as a man of deep principle and decency."