The night before the 2012 Academy Awards, Elizabeth Saltzman didn’t sleep. The next day, she was going to be dressing the actor and wellness entrepreneur Gwyneth Paltrow, who was presenting an award at the ceremony with her Iron Man co-star, Robert Downey Jr.

In spite of having had only a fortnight’s notice that Paltrow would be appearing, 53-year-old Saltzman, her longtime stylist, had found her client the perfect dress. “But I suddenly thought: how could I be so stupid? How could I not have a back-up?’ she recalls. “What if someone drops lipstick on it or throws a cup of tea down it when she’s getting ready?”

Then, she thought: wedding dresses. “Brides never have a back-up dress,” she says. Neither, generally, does Saltzman. However, this dress was different: it was the now-iconic white cape dress by Tom Ford, a perennial on the lists of the best Oscar dresses of all time – and highly vulnerable to all manner of potential pre-award accidents. But Saltzman, a New York native who has lived in London for 18 years (but still works half her time in Los Angeles), stylist to A-listers including Saoirse Ronan, Uma Thurman and Lily Aldridge along with Paltrow, doesn’t “do drama”.

“You frequently have to sew them back into a dress, or cut off the train because they’ve stepped through it, but there’s always a fix, and the world will never know,” she says. “I’ve had customs hold our clothes for [Anna Wintour-organised, New York charity event] the Met Ball and not give them back, so I just went shopping on the day.”

Her calmness under pressure was very much required recently when, a week before Christmas, she found out that another client, Killing Eve star Sandra Oh, was not only nominated for a Golden Globe (which she would go on to win), but was co-hosting the ceremony, alongside Andy Samberg. “That’s not just a red carpet,” says Saltzman. “That’s a red carpet, three changes, and holding the show together – and every fashion house is closed by 21 December.

“People think you have some magical closet that you go into and pull clothes out of,” she says. “But there is a theory behind all of this, and I am old-school – I like to tell a story with my clothes.”

In Oh’s case, “it was also a wrangle because it was for someone who is incredibly talented but still not a household name. I’m sure if one had been calling clothes in for someone else, the doors would have been flung open.”

Saltzman put Oh in Versace, Stella McCartney and Gwyneth Paltrow’s label G, and was universally proclaimed to have slayed it in the styling stakes. And these days that matters. The red carpet, once simply a frothy sideshow – where one could witness Demi Moore in a corset paired with Lycra shorts, or Kim Basinger in a white satin dress she’d designed herself as a tribute to Elvis, complete with a one-armed jacket – has, in the past 20 years, become almost as important as the ceremony itself, synonymous with glamour and big-brand impact.

“For the fashion brand, it’s huge free publicity,” says Saltzman. “And for the talent, a great dress keeps them relevant, and might get them a beauty contract or a fashion contract.” Actors such as Michelle Williams and Jennifer Lawrence have scored enormously lucrative contracts with the likes of Dior and Louis Vuitton, brokered, in part, by their stylists, who have become power players in their own right.

A stylist’s preparations for Oscar night can begin as early as six months in advance. “It all really starts in Venice,” says Saltzman. The city’s annual film festival, in late August, is when industry buzz about potential awards nominations begins in earnest, kicking off an exhausting schedule of events, interviews, lunches and awards show. “People think it’s just about the big four – Globes, SAG, Baftas and Oscars – but once you’re on that campaign trail, it’s so many others: Toronto film festival, Berlin, the Critics’ Choice awards – it doesn’t stop for six months.”

So, it’s really no longer feasible for this year’s best actress nominees Glenn Close or Olivia Colman to make a dash around Selfridges or Bloomingdales for a dress themselves – they would need several new looks, top to toe, each week.

However, with the growth of the red carpet styling business has also come an accompanying explosion in red carpet critique – the next morning’s sometimes brutal best and worst dressed lists. “You can’t please everyone,” shrugs Saltzman. “All I care about is that my clients aren’t getting criticised because of my choices. But I think their skins are a lot tougher than most people imagine.”