Seagate is one of the oldest thoroughfares in Irvine and until the late 16th century it was the main route between the harbour and the town. Here you will find the ruins of Seagate Castle, Irvine’s most ancient remaining structure. There has been a castle in Irvine since the 1180s, which would have been a wooden structure. Irvine’s coastline was further inland coming up as far as Seagate and the town’s medieval harbour was at Seagatefoot.
On the 9th of July 1297 the Treaty of Irvine was signed at Seagate Castle, bringing peace for a while between the Scots and English. A plaque on the remaining ruins commemorates this.
A permanent castle was built in the mid 1300s and was a simple stone tower, incorporating a watchtower for commanding the activities of the harbour. This castle is believed to have been built by Sir Hew of Eglinton who took ownership of the castle in the 1360s.
The castle was remodelled and expanded by the 3rd Earl of Eglinton around the early 1560s. It was not built as a fortified castle and as such was not garrisoned. Designed to be more of a mansion than a castle, it was a place of residence .
A plaque at the entrance of the castle says that Mary, Queen of Scots visited Seagate in 1563 with her four Marys. Although the Earl was a great supporter of Mary, there is no evidence that she visited Seagate.
Various members of the Eglinton family continued to use it until it fell into disuse during the 18th century and Alexander, the 10th Earl of Eglinton had the roof removed. It became a hangout for smugglers and thieves. If anything was stolen from Irvine this was the first place to look! In 1810 the Earl of Eglinton blocked up the doors and windows. A storm in 1839 caused damage and the Earl arranged for a mass of stone to be removed and buried on Irvine Moor.
The remains of the castle are protected as a scheduled monument and in 2011 North Ayrshire Council carried out repair works to strengthen the castle.