Leigh previously held the position of room division manager at Kensington Close, where she was responsible for overseeing the 709-bedroom hotel as it underwent a two-year refurbishment.
She described the Cavendish as "an institution with so much history behind it".
"As one of London's most popular hotels with business and leisure guests, I look forward to being a part of that story," she said. "With plans afoot to improve the facilities and guest rooms, I'm looking forward to continuing the hotel's success this year and beyond."
Rebecca Hollants Van Loocke, regional general manager UK, Germany and Georgia at Ascott, said: "Eva joins our team at a very exciting time. Drawing on her previous experience, she has been brought in to provide stability and continuity to hotel operations as the Cavendish embarks on a series of planned improvements."
At the time of Ascott's acquisition of the hotel from Sir David and Sir Frederick Barclay for £158.8m in 2012, it was announced that the Cavendish would be transformed into serviced residences under the name Ascott St James London. However, a spokesperson for the company said there are no plans to rebrand the hotel in the near future.
Ascott operates six serviced residences in London: Ascott Mayfair, Citadines Prestige Trafalgar Square, Citadines Prestige Holborn-Covent Garden, Citadines Prestige South Kensington, Citadines Barbican and St Marks.
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