The Buckingham Palace garden is opening to the public for picnics and self-guided tours for the first time on Friday.
Such has been the demand for tickets that additional places have been made available on dates throughout July to September.
Tourists will be able to picnic on the sweeping lawns and explore the garden themselves.
The route encompasses the 156-metre Herbaceous Border, the Horse Chestnut Avenue, plane trees planted by and named after Queen Victoria and Prince Albert, and views of the island and its beehives across the 3.5-acre lake.
A new range of summertime picnic-inspired products has also been launched by the Royal Collection Trust to coincide with the opening at the Queen’s London home.
Featuring a design inspired by royal ceremonies and summer flowers, items include a picnic blanket, a sandwich bag, cotton napkins and a reusable water bottle.
The sandwich bag, priced at £7.95, features colourful motifs of corgis, cupcakes, carriages, butterflies, flowers and soldiers in red tunics and bearskin hats.
The Buckingham Palace hand sanitiser, decorated with a mauve crown and two sprays of flowers costs £3.95, while the pale blue picnic rug, priced at £35, is rolled and secured with a floral fastening which is also decorated with a blue and white china teapot.
Strawberry and champagne jam and buttery shortbread biscuits are among the treats being sold by the Royal Collection.
The 200g Strawberry and Marc de Champagne Preserve costs £4.95, a tin of Buckingham Palace orange and lemon shortbread is £6.95 and a white cotton napkin embroidered with a gold fork and spoon is £8.95.
Members of the public, who must pre-book, can also pre-arrange to join guided tours around the south west of the garden including the Rose Garden, summer house and wildflower meadow.
Adam, 25, a visitor services warden for the Royal Collection, said of the garden opening: “It’s an offer that we’ve never offered before.
“It’s an exciting prospect to allow people to come in and picnic in the gardens and explore to their own leisure.
“We’re sort of in an oasis within the centre of London so not many people realise it’s here or how big it is either. It’s the largest private garden in London, so I feel like we’ve got lots of secrets to tell people.”
He said of the Queen, who receives a seasonal posy made from the garden’s blooms each week when she is in residence: “She definitely likes to be involved with everything that’s going on.”
Sally Goodsir, the Royal Collection’s curator of decorative arts, said: “We sadly haven’t been able to open the state rooms this year because of the current situation as we might ordinarily have done and therefore it’s wonderful to be able to open the garden instead.”
She explained how the garden was steeped in history, with George III’s consort Queen Charlotte once having a menagerie on site including a zebra.
Meanwhile, Victoria and Albert had designed a more naturalistic garden, with the latter nearly drowning while ice-skating on the lake in 1841, but being rescued by his wife.
Daily talks by visitor services wardens and trails for families are included as part of the general visit.
Art and craft activities will be available for those with children on Mondays in July and August, from July 19, and as part of two Family Festival days on August 26 and 30, with warden-led family tours.
The current landscape of the historic 39-acre garden dates back to the 1820s when George IV turned Buckingham House into a palace.
Despite its urban location, the garden is home to rare native plants seldom seen in London, more than 1,000 trees, 320 different wildflowers and grasses, and the National Collection of Mulberry Trees.
Its Rose Garden contains 25 beds of roses, and each bed is planted with 60 rose bushes of a different variety, and no two adjacent beds are of a similar colour.
Since 2008 the island in the lake has been home to five beehives, which produce around 160 jars of honey a year for use in the royal kitchens.
Some of the garden’s botanicals including lemon verbena, hawthorn berries, bay leaves and mulberry leaves are used to make Buckingham Palace Gin, which is sold by the RCT.
The traditional summer opening of the Palace’s state rooms and themed exhibition, which normally welcomes thousands, was cancelled for a second year due to the pandemic.
Traditionally, the Queen also hosts 8,000 guests at a time at three Garden Parties a year at the Palace, but this year’s and last were also unable to go ahead.