Prince Charles at Wick Old Church, Wick, on Sunday
Prince Charles has said he was "flattered" after receiving the Freedom of Caithness.
Since the Queen Mother's death, he kept up connection with the Castle of Mey, her former private home.
The honour was bestowed on him by Highland Council during an event at the Assembly Rooms in Wick.
The prince, who turns 60 in November, described the freedom as one of the best early birthday presents he could receive.
He also expressed his disappointment he could not have shared the news of his "enormous honour" with his grandmother.
The prince said: "I can't tell you how touched I have been by the news you wished to do this.
"I could not be more flattered, and indeed grateful to Highland Council for what has turned out to be probably one of the best early 60th birthday presents I could receive."
Prince Charles, who wore a kilt, spoke of his childhood memories of arriving in Scrabster on the Royal Yacht Britannia and being driven to the Castle of Mey.
He said: "There was something tucked away in my heart for a very long time in this part of the world.
"As many of you will know, I adored my grandmother, and one of the most frustrating things about today is that I cannot ring her up and tell her about it."
Prince Charles has continued to actively promote the area nationally, through his North Highland Initiative.
He attended a service marking the centenary of the Territorial Army at Wick Old Church on Sunday.
The Queen Mother was granted the Freedom of Wick in 1956 and The Freedom of the District of Caithness in 1990.