Use Gatwick as a transit point rather than a dead end. From Brighton, the Thameslink takes 30 minutes to Gatwick; from Gatwick, one change and 30 minutes more puts you in Windsor. The castle, the Long Walk, and the Thames. Then Heathrow from Windsor the following morning.
Getting There
Thameslink from Brighton to Gatwick takes approximately 30 minutes. From Gatwick, take the train to Slough (South Western Railway or Great Western, approximately 35 minutes), then change to the short Windsor branch line to Windsor and Eton Central (5 minutes). Alternatively, from Gatwick take the South Western Railway to Windsor and Eton Riverside via Weybridge (approximately 55 minutes direct).
Total journey Brighton to Windsor: approximately 90 minutes with changes.
Windsor Castle
Windsor Castle is the largest occupied castle in the world and the oldest continuously occupied royal residence. The State Apartments, St George's Chapel, and the Semi-State Rooms form the main visitor circuit. St George's Chapel contains the tombs of ten monarchs including Henry VIII and Charles I.
Entry is approximately £27.50. The castle grounds are extensive but largely flat. Allow 3 hours for the full circuit. Closed on some dates when the Royal Family is in residence - check the Royal Collection Trust website before visiting.
The Long Walk
The Long Walk is a 4.8-kilometre straight avenue of plane and chestnut trees running south from the castle to the Copper Horse statue of George III on Snow Hill in Great Windsor Park. Flat, wide, and largely free of steps. At post-marathon pace, walking to the Copper Horse and back is the morning programme - approximately 10 kilometres and as much time as the legs permit.
The Thames
Windsor bridge crosses to Eton on the opposite bank, with Eton College's buildings visible from the bridge. The Thames Path along the river bank in both directions from Windsor is flat and accessible. In April the river is running high after winter; the bankside walk toward Boveney Lock (2 kilometres upstream) and back is the afternoon option.
Where to Stay
The Castle Hotel Windsor on the High Street is directly opposite the castle. Macdonald Windsor Hotel on High Street is comfortable and central. Both require advance booking for April weekends.
Getting to Heathrow
First Great Western from Windsor and Eton Central to London Paddington takes approximately 35 minutes (via Slough), then Elizabeth Line from Paddington to Heathrow Terminal 2, 3, 4 or 5 takes 25 minutes. Total journey Windsor to Heathrow: approximately 60 minutes.
Alternatively, direct bus services operate between Windsor and Heathrow (approximately 30 minutes). The First bus company runs the 702 service from Windsor High Street to Heathrow Central Bus Station.