A true copy of artwork by Charles Rennie Mackintosh's wife has returned to the historic Willow Tea Rooms Building, completing a £10m restoration.

An exact replica of the original Gesso Panel, a sculptural relief created by Mackintosh's artist wife, Margaret Macdonald, has been recreated and returned to its former home.

Celia Sinclair, chairwoman of The Willow Tea Rooms Trust, commissioned a copy to be built by artists Dai and Jenny Vaughan, which was revealed on Tuesday.

The historic panel was originally the central feature in the Salon de Luxe at the Willow Tea Rooms Building.

The original piece was moved to the Kelvingrove Museum while the £10m restoration took place at the building on Sauchiehall Street in Glasgow's city centre.

Charles and his wife Margaret were at the height of their artistic careers when the Willow Tea Room Building opened in 1903.

Artist Ms Vaughan said: "This is one of the most complex items of work Dai and I have ever undertaken.

"Mackintosh believed that the Gesso Panel was the heart and soul of his interiors.

"I admire Margaret MacDonald as she put so much detail into her work.

"We were lucky and were able to use a modern icing gun to create the lines and patterns on the panel.

"Margaret MacDonald would have had to use an icing bag, which is much harder to control.

"Her technique was unique and it has been our greatest challenge to recreate her masterpiece."

The A-listed Willow Tea Rooms Building is recognised internationally as the only surviving tea room designed in its entirety by Charles Rennie Mackintosh.

"The return of the Gesso Panel represents the final piece of the four year, £10m restoration project of the Willow Tea Room Building on Sauchiehall Street," said Ms Sinclair.

"The board of trustees, the advisory panel and all the specialist glassmakers, furniture makers, builders and artists have worked extremely hard to recreate the building."

The full 200-seat restaurant and tearooms, known as Mackintosh at The Willow will officially open in September 2018.

When fully open, it is estimated the Tea Rooms Building will welcome at least 360,000 visitors a year, with a predicted annual turnover of £3m.

It will operate as a social enterprise and hub for Glasgow, creating 40 full-time jobs, plus additional volunteer and work experience and training opportunities.

Mackintosh at The Willow will include the ground floor Front and Back Saloons, Gallery, Billiard Room and the opulent Salon de Luxe plus exhibition, retail, learning and education and conference suite in the adjoining building.

In June, the Mackintosh Glasgow School of Art was struck with a major blaze, devastating it and nearby buildings.

The building was undergoing a multimillion-pound restoration after it was partly destroyed by a fire four years before, which resulted in the loss of the celebrated Mackintosh Library.