William Tyrrell's gran has lost hope

The grandmother of missing NSW toddler William Tyrrell says she has given up hope the boy will be found 18 months after he disappeared.

Natalie Collins, 56, said she had been devastated by the loss of the three-year-old, who was last seen wearing a Spider-Man costume at the home of another relative in Kendall on the mid-north coast.

"I wish he was alive, but I dont think he is," she told the Daily Telegraph on Tuesday.