The Royal barge will be decked out with nearly 10,000 flowers and 600 plants as it carries the Queen down the Thames.

The floral extravaganza, made up of 4000 red carnations, 2100 Darcey roses, 1000 Patience roses and 500 purple and red sweet peas, will see the Queen and the Duke of Edinburgh surrounded by a sea of colour as they are transported along the river on Sunday.

The Duke and Duchess of Cambridge will be at the Queen's side as she receives the well wishes of up to a million spectators expected to line the river banks and open spaces.

The Prince of Wales, Duchess of Cornwall and Prince Harry are also expected to be on the barge.

Five varieties of herbs will be used to create a scented English country garden on the barge, with 300 bunches of English lavender, 20 bunches of rosemary and 100 bunches of bay to make the vessel a feast for the eyes and nose.

The creation has taken 20 gardeners seven months to plan and grow. About 45 florists, gardeners and flower arrangers have spent a week decorating the barge.

A giant "E" for Elizabeth has been formed from 1500 St Paulia flowers and 400 Patience roses, while a knot garden featuring 200 clipped, mature box plants has also been made.

Ninety garlands, each about two metres tall, will festoon the vessel. The plants include 20 Scottish thistles, 60 Welsh daffodils and 20 varieties of Commonwealth species.

Gardening presenter Rachel de Thame has created the floral designs for the royal barge, a luxury cruiser called the Spirit of Chartwell, with the help of Mark Fane, who has built 20 gold medal-winning gardens at the Chelsea Flower Show and floral designer and artist, Kitty Arden.