welcome to celebrity world: Daring duchess, winner in the glamour stakes at War Horse premiere

By Rebecca English, Royal Correspondent

The Duchess of Cambridge opted for a creation by Alice Temperley – fit with a plunging neckline and fishtail

For a wet January night on the red carpet it was both risky… and, some might say, a little risqué.

But on the eve of her 30th birthday, the Duchess of Cambridge wasn’t about to melt into the background in something basic.

Instead she chose a daring black lace and nude creation by Alice Temperley – fit with a plunging neckline and fishtail.

Thanks to her well prepared husband and his trusty umbrella keeping her dry, Kate triumphed last night at her first royal film premiere.

She and William were guests of honour at the UK launch of Steven Spielberg’s latest film, War Horse.

The duchess’s co-star on the red carpet was the film’s equine leading man – a chestnut colt called Joey, who had his own PR and personal ‘manure scooper’ (with good reason).

Kate will celebrate her landmark birthday today privately with family and friends. St James’s Palace said it would be ‘a low key celebration’, but last night was very much about glamour.

Classic elegance: Kate's sylph-like figure was exhibited to stunning effect in the beautifully embroidered dress

All in the detail: Kate has exhibited a fondness for lace before, and the delicate outer layer of her skirt certainly made for a beautiful finish

The premiere at the Odeon in Leicester Square was being held in aid of the charitable Foundation of Prince William and Prince Harry, of which Kate is a patron.

The couple met members of the cast including Jeremy Irvine, Benedict Cumberbatch, David Thewlis and Emily Watson as well as Spielberg.

Irvine, the 21-year-old Cambridge-born lead in the film, said: ‘This is a long, long way from where I grew up. The fact that they’re here to watch my fat face on a cinema screen is bizarre.

‘It’s such a thrill. I am beyond excited.’

Hundreds of serving and ex-serving military personnel associated with William’s official regiments were also in attendance.

Based on Michael Morpurgo’s novel, War Horse tells the story of a remarkable friendship between farmhand Albert and an ‘untameable’ young colt, Joey who are forcibly separated by the First World War. Like the book, it also focuses on the atrocious conditions horses endured in the Great War.

Director Steven Spielberg spoke about the couple's gesture in attending the event, saying: 'It's a very prestigious honour because they represent an entirely new era in British royalty that has the entire world excited.

'When they came to America, that was one of the most exciting events, I think, that we've enjoyed for some time, so it's such an honour to be here in the UK to be able to meet them and to be able to show them, and all of us, War Horse.'

Belle of the ball: Kate Middleton lead the way at the War Horse premiere in Leicester Square with a stunning floor-length gown, as Prince William shielded her from the rain

Keeping her dry: The gallant Prince ensured Kate's outfit was untouched by the driving rain

'I am delighted that the UK Premiere of War Horse is in aid of ‘The Foundation of Prince William and Prince Harry’ and that this special occasion is attended by two of the patrons, Their Royal Highnesses, The Duke and Duchess of Cambridge.'

'War Horse encapsulates for me a timeless personal story of courage. The movie, which I am proud to say was filmed here in Great Britain, deals with the discovery of humanity against conflict, and celebrates bravery, loyalty, tenacity and hope.'

'We are honoured to dedicate this event in aid of the Foundation which recognises the welfare of those who serve their country in the British Armed Forces.'

Six hundred serving and ex-serving military personnel and their families are also attended the premiere, alongside beneficiaries of military charities, with which the Foundation of Prince William and Prince Harry has been working.

The servicemen and women have been invited from The Duke of Cambridge’s regiments, including RAF Search and Rescue, Household Cavalry, Irish Guards, Royal Air Force Coningsby, Scotland Royal Naval Command and Submarines Royal Naval Command.

Meanwhile, Tom Hiddleston, who plays Captain Nicholls in the film, has admitted that he lied about how competent a horse rider he was when he signed up to the project.

He said: 'I claimed to ride "competently" but in reality I looked more like Billy Crystal at the beginning of 'City Slickers' than a cavalry officer: heels out and sitting back like a sack of potatoes, as though I was riding some kind of living motorbike. Hopeless.

'The grooms and stuntsman, the best in the world, quickly disabused me of my bad habits: drill for four hours a day for five weeks, "Heels down! Elbows! Hands to you! Sit up straight! Shoulders back!" '

High spirits: Kate celebrates her 30th birthday tomorrow, but is not expected to mark the occasion with a lavish party

Always gracious: Kate looked delighted as she received a bunch of flowers from a young fan

Time to celebrate: The Duke and Duchess of Cambridge were later seen arriving at the premiere afterparty, held at the Queen's Gallery

Good spirits: The couple appeared to be thoroughly enjoying themselves as they arrived for the party

Also on the carpet: Emily Watson and Cheska Hull both looked lovely in full-length dresses

Blushing red: Celine Buckens, in a £595 Victoria, Victoria Beckham dress, and Downton Abbey star Jessica Brown Finlay both looked stunning in their vivid colour choices