Sometimes, the small things are what make a house a home, no matter how grand its walls. Today, President Michael D Higgins and his wife Sabina will enter Windsor Castle with Queen Elizabeth and the Duke of Edinburgh. Inside the sovereign's entrance are four small statues of corgis, visible if one knows where to look – a homely gesture by a monarch who has kept the breed since she was a child.

During her 60 years on the throne, heads of state have come to visit London twice a year, staying in Buckingham Palace. Only fellow royals and much-loved foreign leaders, such as Ronald Reagan, have been favoured with Windsor.

The town is bedecked in Union flags and Tricolours, a sight unimaginable even a few years ago. Traffic here will remain gridlock-free over the next four days as the Higgins party comes and goes.

The presidential couple will be met before 10am at the Irish embassy on Grosvenor Place by Prince Charles and Camilla, Duchess of Cornwall. From there, Mr Higgins and Prince Charles will travel in the royal Bentley to Windsor, with the duchess and Mrs Higgins travelling behind. The rest of the party will form a motorcade that will be escorted through busy streets to Windsor.

The greeting by Prince Charles, rather than by the queen, complies with rigid royal protocols that have been drawn up over centuries and now stand immutable. Near Windsor's railway station, the party will be met by the queen and Prince Philip, Duke of Edinburgh, along with the sovereign's escorts – the troops from the Household Cavalry and the Mounted Band of the Lifeguards.

The Royal Salute will be played, along with Amhrán na bhFiann , before the royal and presidential couples are escorted to horse-drawn carriages by the master of the horse, Lord Vestey, for the short journey to the castle.

Both anthems will be played again as the carriages move off through Windsor: the queen and President will travel in the first, followed by the Duke of Edinburgh and Mrs Higgins in the second. The route will be lined by soldiers from the guards' regiments: the Grenadiers, the Coldstream, the Scots and the Welsh. Although the Irish Guards are currently on service in Cyprus, a few will be present.

Inside, lunch will be followed by an inspection of items of Irish historical significance held in the royal collection. Later in the afternoon, Mr Higgins will travel to Westminster, where he will lay a wreath at the Tomb of the Unknown Soldier in Westminster Abbey. "For all anyone knows, the unknown soldier may well have been Irish," says Irish Ambassador Dan Mulhall.

For some, this will be seen as a reciprocal offering for the queen’s decision to bow her head at Dublin’s Garden of Remembrance three years ago.

The President will then address peers and MPs at the royal gallery in the Palace of Westminster. Most of the attention will be focused on this evening's white-tie state banquet at Windsor Castle, where Sinn Féin's Martin McGuinness will be one of 200 people attending. Formal photographs of the royal party, which will include Mr and Mrs Higgins, will taken as they enter the castle's grand reception room, before the guests are introduced by the Lord Steward.

No photographs of the queen shaking hands with Martin McGuinness will be taken, which is again in line with royal protocol. Even though this won’t be their first handshake, McGuinness may be glad such a memento will not be available this time.