(CNN) Prince Harry and world-renowned primatologist and conservationist Jane Goodall greeted each other on Tuesday in unorthodox fashion.

The Duke of Sussex gave Goodall what's known as a "chimp greeting" by bending down and patting her on the head before the two hugged.

Video: Dr Jane Goodall @JaneGoodallInst asked #princeharry if he remembered the "chimp greeting" from when they first met in Dec (& last month). They brilliantly re-enacted it: Jane as the nervous female approaches and Harry pats her on the head to encourage her for a hug! 🐒 🐵 pic.twitter.com/gKAxJOqPY5 — Emily Andrews (@byEmilyAndrews) July 23, 2019

Goodall's environmental program Roots & Shoots is currently holding its sixth global leadership gathering at the castle, and Prince Harry stopped by to meet 26 students.

"As my grandmother The Queen once said, 'Sometimes the world's problems are so big we think we can do little to help,'" the Duke said on Tuesday. "On our own we cannot end wars or wipe out injustice, but the cumulative impact of thousands of small acts of goodness can be bigger than we imagine."

The duke, who often participates in conservation efforts , attended a Tuesday meeting and listened to presentations on endangered species and reducing plastic waste before greeting the students.