A pioneering Oxford hospice is set to receive a anniversary fundraising boost, thanks to a Royal Command concert in London.

Helen and Douglas House, in Magdalen Road, East Oxford, is bringing its 25th anniversary year to an end in style - with a concert which will be attended by the Prince of Wales and the Duchess of Cornwall.

Helen House was the first children's respite hospice in the world when it opened in 1982.

It has held a year of fundraising and celebration events to mark its landmark birthday, which will climax with a concert at St John's Church, in London's Smith Square, on Wednesday.

Sister Frances Dominica, who founded the hospice, will say a few words to introduce the London Chamber Orchestra concert, which will include the first London performance of a piece of music commissioned by Prince Charles in memory of his grandmother, the Queen Mother.

Sister Frances said: "There can be no greater tragedy than to know that your child has a life-shortening condition.

"Personally, I have fewer answers to the big questions than I had 25 years ago.

"But I do believe that by offering friendship and practical help in whatever way is most appropriate for each unique child, young person and family, we can do something worthwhile.

"We are immensely grateful to the Prince of Wales, and to our patron the Duchess of Cornwall, for honouring us with their presence at this special concert, as well as to the London Chamber Orchestra and St John's."

Last December, the Duchess invited a group of children from Helen House to help her decorate the Christmas tree at the Royal couple's London home, Clarence House.

A group of staff, carers, guests and families from Helen and Douglas House will be attending the concert and a block of VIP seats has been allocated, some of which have been sold to raise funds for the charity.

Among those attending will be Steve and Sarah-Jayne Dawes, whose daughter, Freya, used to go to Helen House before her death in 2004.

Mrs Dawes said: "When we first went into Helen House it felt as if a very heavy overcoat had been taken off my shoulders. The whole place was bright and cheery."

Helen and Douglas House fundraising manager Joanna Mitchell said: "We are very excited. We hoped the Duchess of Cornwall, as our patron, would be able to attend and we were absolutely delighted when we heard the Prince of Wales was going to be able to come along as well."

It has been sponsored by Japanese charity Momiji, which has been supporting Helen and Douglas House since organising a trip to Japan for children, young adults and families in 2005.