As Prince Charles's personal harpist, Hannah Stone performs in palaces and Royal retreats.

Before making her strings sing to the strains of Bach, Schubert and Ravel at King's Lynn Festival last night, the acclaimed musician dropped in on the factory where they make them.

Lynn-based Bow Brand International, which sponsored the concert at All Saints' Church, is one of only five companies in the world which make harp strings from cow gut.

Miss Stone, 26, was taken on a tour of the factory – on Highgate – by production manager Rosina Russell.

'I never knew what went into them,' she said, as she saw gut being soaked, stretched, spun and dried on different floors of the factory.They are the best.'

Miss Stone, from Swansea, was appointed Prince Charles's harpist in 2011. She said she realised by the age of 14 or 15 that she wanted to be a musician.

'There's definitely an affinity for me, it's the national instrument of Wales,' she said. 'Being a musician can be quite lonely but a harp has a big presence – they all have their own individual qualities.'

Carolyn Clarke, managing director of Bow Brand, said the company was established in 1902 and was the only factory of its kind in the UK.

'We were here when this was just fields and they used to drive the cattle up the A10 to the cattle market,' she said. 'I guess they thought: 'We'll just build a factory and steam the intestines here'.'

During the two world wars, Bow Brand made sutures for stitching wounds – those made of gut dissolve gradually as the injury heals.

Mrs Clarke said the company, which employs 25, was having its busiest ever year.

'I thought we'd be affected by the recession because we're a luxury item,' she said.

Alison Croose, chairman of King's Lynn Festival, said: 'Carolyn is a very keen supporter of the festival and there's this wonderful link where Bow brand have sponsored a concert by the Royal harpist and the harp's strings are made here.'