William and Kate told of Spice devastation

The Duke and Duchess of Cambridge have been moved by the devastation caused by the synthetic drug Spice during a visit to a homelessness charity he first visited with his late mother.

The couple heard that increasing numbers of rough sleepers are becoming addicted to Spice, which can leave users in a "zombie-like" state.

The duke and duchess were touring a London centre run by The Passage.

Also known as Mamba, Spice was outlawed two years ago.

William first visited the charity in 1994 with his younger brother Harry, when the pair were 12 and 10, alongside their mother Diana, Princess of Wales.

The Passage's chief executive Mick Clarke praised the couple's "real empathy".

"They very much care about the issue and I think it marks the way they care about the poorest in society," he said.

During the visit the duke told Mr Clarke: "The fact it was a legal high and that young people were allowed to take it and it leads to addiction is just terrible."

The charity said a survey of its homeless clients this year found that 70% had tried Spice - up from 50% when similar research was carried out two years ago.

Earlier in the day, the duke and duchess visited Evelina London Children's Hospital following the announcement that the duchess was to become its new patron.

The Evelina is part of Guy's and St Thomas' NHS Foundation Trust, of which the Queen is Patron, and treats children with complex and rare conditions from birth into adulthood.

The duke and duchess both got involved in Christmas crafting with some of the families in Evelina's atrium.