Prince Harry is to have his royal title dropped from the credits of an exhibition at Kensington Palace showing the dresses of his mother Diana, Princess of Wales.

A week ago, the Diana exhibits came with a display panel that said “Lent by HRH [his royal highness] the Duke of Cambridge and HRH the Duke of Sussex”, the Sunday Times reported. But Harry’s HRH is to be removed with its inclusion blamed on “an administrative error”.

The changes reflect the continuing sensitivities over Harry’s departure from royal life and his move, with wife Meghan and son Archie, to California.

Under the arrangement it was agreed the Duke and Duchess of Sussex could retain their HRH styles, but the couple has agreed not to use them. That is in contrast to Diana, who was stripped of her HRH title after her divorce from Prince Charles.

The panels at Kensington Palace are on the star exhibits in an exhibition that opened last week titled Royal Style in the Making.

It includes Diana’s 1981 wedding dress, designed by David and Elizabeth Emanuel, complete with its spectacular sequin encrusted train which, at 25ft, filled the aisle of St Paul’s Cathedral. It remains the longest in royal history.

Also on display is the pink suit with ruffle detail created by designers at Bellville Sassoon, which Diana wore as she departed on her honeymoon. She wore it on several other occasions, including the royal couple’s 1983 tour of Australia.

Both are being loaned by William and Harry. In a sign of the protocol messiness that is likely to continue, Harry is still called HRH Duke of Sussex on the Kensington Palace website page for the new exhibition.

The loans were organised by the Royal Collection Trust. In a statement, it said the dresses were “loaned by HRH the Duke of Cambridge and the Duke of Sussex” and that “due to an administrative error, for which the Royal Collection Trust was responsible, the labels were incorrect and will be updated”.