He begins at the summer garden party where 8,000 people are invited on to the grounds, and meets beekeeper John Chapple as he harvests honey. He also explores the garden's origin, learning it was part of Henry VIII's hunting ground, and views the Rose Garden in late summer. As autumn arrives he watches the lawn being prepared for a special football match, and meets deputy gardens manager Claire Midgley-Adam as she battles to save a tree planted by the Queen's father George VI. He then helps royal florist Sharon Gaddes-Croasdale prepare the palace with holly and mistletoe at Christmas.

In winter, there are fewer tourists at Buckingham Palace, but Alan Titchmarsh discovers all manner of animal visitors to the grounds as he installs hidden cameras in trees and bird boxes. As spring arrives early, he learns about the garden's role as a nursery, not just to young animals but also to young royals. In late May, a transformation takes place - a tented village on the lawn is a sign that party season is coming, and the race is on for the gardeners to put the finishing touches to 12 months of work. The programme ends with the climax of the year, as the Queen attends a garden party to greet her guests.