We were staying at the Grand Hotel Casselburgh just a few minutes walk up the road and was recommended this by our hotel reception team, we hadn't reserved anywhere for a Saturday night and wanted to avoid the main touristy square. We didn't think we'd have much luck but she phoned ahead and they'd had a cancellation so we opted to go (only realised afterwards it had been on our radar via TA as one of the Michelin restaurants!)
We were welcomed quickly and settled at our table. We opted for the scallops and tuna carpaccio to start and then followed it with moules frites. We were too full for dessert but spied some nice dishes on other tables. The service was prompt, attentive and polite and the atmosphere was good for a late Saturday evening. We especially loved the fish tank with lobster and oysters which gave us the reassurance the food would be fresh :)
Would definitely recommend but it's mostly fish on the menu so just be conscious before you go along.