Highmore, who starred with Depp in Finding Neverland and Charlie and the Chocolate Factory, told Digital Spy that he has great personal and professional respect for the Hollywood icon.
"In terms of acting, he's phenomenal - the range of characters he can play," the 18-year-old commented.
"What really stood out to me is just how great a person he is and how great a friend he's been to me. He's brilliant!"
The film opened in the US in June and arrives on UK screens this Friday.
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