The head teacher said the royal helper had been "really chatty" with the children on the bus, playing I-spy with them and helping with their jumpers. The children were visiting a trail around the gallery encouraging them to think about their emotions, linked to Catherine's early years education project, Shaping Us.

The Princess of Wales was reportedly “animated” and “nurturing” with the little ones during Tuesday’s National Portrait Gallery outing.

The National Portrait Gallery, of which she is royal patron, recently launched the free exhibition to encourage young children to understand and express emotions.