The Duke and Duchess of Cambridge were 130 miles apart, but they spoke with one voice as they chatted to children, parents and health professionals.
For William, it was also a chance to indulge his love of aircraft, an affair that had begun in Yorkshire 10 years ago, when he trained at with the RAF at Linton-on-Ouse. His uniform identified him then as Flying Officer Wales.
Yesterday he climbed into the cockpit of a Typhoon jet at RAF Coningsby in Lincolnshire – a base from which he had also flown.
It is one of two which provides 24-hour fighter cover to intercept threats ranging from Russian bombers to commercial airliners suspected to have been hijacked.
But it was the children of the air crews, at the base’s new “engagement centre” who seemed to most entrance him. Did they want to be pilots in the RAF, he asked.
When one girl replied that she wanted to be an engineer, William said: “We need lots more girls as engineers. They’re very, very good.”
It was the kind of resolve that Kate was also seeing, as she opened a new London headquarters for the charity, Place2Be, which, she said, was leading efforts “to give every child the very best start in life”.
The Duchess said: “School leaders and teachers need expert guidance and training to develop their own approaches to supporting children’s mental well-being.
“They also need access to a pool of experienced, well-trained mental health professionals, who can step in when things are more complex or serious.”
Kate became patron of Place2Be five years ago and has become closely involved with its attempts to provide early intervention for children before problems escalate.
Last week,sharing a platform with Prince Harry and his fiancée, Meghan Markle, she also spoke in support of the Heads Together mental health initiative which all four young Royals are supporting.
At yesterday’s event, Kate, who is expecting her third child next month, joined three pupils from Albion Primary School in Rotherhithe, London, where Place2Be has been providing mental health support for pupils, families and staff for 16 years.
The youngsters had been given a drawing of a hand and had been writing the qualities of good friendship along the fingers.
The Duchess wore a Marlene maternity cocktail dress by Seraphine – one she had also worn in Norway last year.