Pippa Middleton, The Duchess of Cambridge???s younger sister, took an evening off from wedding planning last night to attend the ParaSnow Ball on the arm of her fianc??James Matthews.

It is the first time that the couple have been photographed together officially since Christmas Day when they attended church with the Middletons and the Cambridges.

Last night???s outing suggested that Middleton is upping the ante, style-wise in the run-up to her wedding.She opted for a ??1,735 cornflower blue dress with crystal embellishments by Erdem, the London fashion week designer renowned for his delicate, opulent and ultra-ladylike designs.

The ???Heta??? dress, which is from the Resort 2017 collection and inspired by the meeting of Japanese and Western cultures, also served to highlight the toned arms which Middleton has no doubt been honing in the run-up to her wedding.

Pippa is set to marry James Matthews, a hedge fund manager and brother of Made in Chelseastar Spencer Matthews, at St Mark"s Church in Englefield, near to the Middleton family home in Bucklebury on 20th May.

It"s set to be the society wedding of the year, with The Duke and Duchess of Cambridge, Prince Harry and Meghan Markle in attendance.Prince George and Princess Charlotte will have starring roles as page boy and bridesmaid.Last week, Pippa was seen visiting the church with parents Carole and Michael, no doubt to make final preparations for the big day.

Middleton???s look last night was one of her most sophisticated and grown-up yet, suggesting she may have been seeking Kate???s guidance in all matters sartorial.

Erdem is one of The Duchess???s clutch of go-to designers.Most recently, she chose his sleek ???Evita??? shift dress for a Heads Together briefing in January but her wardrobe contains several coats, dresses and evening gowns by the designer.

Speculation is mounting regarding the identity of the designer behind Middleton???s wedding dress.Erdem would be a no-brainer contender for the commission given his mastery of high-stakes dresses and a natural affinity for the bucolic styles which work so perfectly for English country weddings.

Kate first wore Erdem soon after she married in 2011; the fitted navy lace dress she debuted during her first visit to Canada was seen as one of her first smart diplomatic fashion choices as Erdem Moralioglu was brought up partly in Montreal before studying in Toronto.

Kate and Pippa aren???t Erdem???s only high-profile fans.He has become a favourite amongst English rose-types with Claire Foy (who plays The Queen in The Crown), Jenna Coleman, Sienna Miller and Keira Knightley amongst his most faithful acolytyes.

Prince Harry???s girlfriend Meghan Markle also chose a floor-sweeping, bird printed Erdem dress for the wedding of Tom Inskip and Lara Hughes Young which she attended with Harry in March.

Pippa Middleton grid

Middleton???s choice last night also marked a significant departure from the low-key but always polished style for which she has become known.In contrast to the high fashion pieces favoured by The Duchess for glamorous engagements, Middleton has often stuck to affordable labels or more simple pieces from designer labels such as Temperley or Jenny Packham.

At the Frost summer party which she attended last summer on the evening before her engagement was announced, she wore an L.K Bennett floral dress and in the week that followed, she was seen in numerous affordable high street looks by the likes of Vila and Whistles.

Among the other contenders for Middleton"s wedding dress designer are Jenny Packham, Alice Temperley, Ralph and Russo and Emilia Wickstead.

For Princess Charlotte???s christening last year, Middleton wore an elegant white outfit by Emilia Wickstead, another Duchess of Cambridge favourite.She isamongst the runners and riders for the job, especially because she has already quietly established a bespoke bridal business.This week, Wickstead launched her first ready-to-wear bridal collection in what could prove to be a savvy move if she is behind the wedding dress of the year.

All will be revealed on 20th May.

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