During the summer months (June to August), the sun reaches its highest point in the sky around 1:00 pm BST (British Summer Time). In the winter months (December to February), the sun is highest in the sky around 12:00 pm GMT (Greenwich Mean Time).
It's worth noting that the UK observes Daylight Saving Time (DST) from the last Sunday in March until the last Sunday in October, during which time the clocks are set one hour forward. Therefore, the times mentioned above are based on standard time (GMT or BST) and may differ from the actual time on your local clock during the summer months.