Queen Camilla‘s grandmother has been revealed as an unlikely pioneer of dressing up for Halloween – alongside Princess Diana‘s step-grandmother Barbara Cartland. Sonia Cubitt, née Keppel, is seen in newly-unearthed photographs modelling a spooky ‘Three Candles’ costume for a Halloween ball back in October 1930. She was one of 13 society ‘It Girls’ of the era who donned outfits specially designed by novelist Dame Barbara for what was dubbed a ‘Pageant of the Superstitions’ special at London‘s Park Lane Hotel. The women – including Dame Barbara herself – appeared at midnight on October 31, 1930 at the ball, which has since been described as Britain’s first major fashion showcase of its kind. It was an early example of people this side of the Atlantic putting on Halloween party attire. The photos have emerged as modern-day revellers across the country – as well as celebrities at elaborate parties – will be doing similar tonight for Halloween. The list of models and their outfits’ titles were shared by Dame Barbara’s granddaughter Tara McCorquodale, who told MailOnline: ‘My grandmother loved to dress up and designed many wonderful creations including all the sensational dresses at the Superstitions Ball. ‘Always an optimist, she took no chances and went as “Good luck” – contributing to the invention of Halloween costumes, as we know them today, is an accolade she would have worn proudly

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Sonia was one of the daughters of Camilla’s great-grandmother Alice Keppel, who had been the mistress of King Edward VII.Dame Barbara was the mother of Raine Spencer, who became Princess Diana’s stepmother when she married her father Earl Spencer in 1976.   The author died aged 98 in 2000. More than 750million copies of her books have been sold around the world.In 1930, she was tasked with coming up with 13 outfits that would give a quirky spin on unlucky concepts.The clothes were made by the theatrical costume company L & H Nathan Ltd.Sonia’s was inspired by the superstition that three candles should never be lit as the person closest to the shortest one would supposedly then be the first to either marry or die. Dame Barbara herself – then described in contemporary reports as Mrs A. G. McCorquodale, in reference to her then-husband – wore an over-sized horseshoe on her head to symbolise good luck. Other models included Miss Mary Pitcairn as a witch, the Countess of Carlisle as a broken mirror, the Hon. Mrs Parsons marking the number 13, Lady (Hamilton) Grant as ‘Upsetting The Salt’ and the Hon. Mrs John Russell depicting ‘Friday’.  The Princess George Imeritinsky’s defining feature was being green, Miss Carl Bendix represented a single magpie while Miss Betty Hulton’s outfit was based on crossed knives.