The Duchess of Cambridge revealed that Prince George is growing up fast as she accepted the gift of a personalised babygro from a young ex-offender today.
His daughter, 20-month-old Teegan, tried to take the present back from Kate - leading her to sympathise with Mr Russell-Andrews about how demanding babies can be.
Only Connect, a crime prevention charity that works with prisoners, former criminals and young people at risk of offending, had invited the royal couple to see their headquarters to learn more about what they do.
At a nearby Only Connect venue, OC Central, the pair were treated to contemporary dance performances by the group Dance United and had the opportunity to meet those connected to the charity, including Mr Russell-Andrews and his little girl.
Mr Russell-Andrews, 22, from Camden, north London, became involved with Only Connect four years ago after committing a crime a day as a teenager - including robbery, burglary and vehicle theft - and is now a professional actor.
He said: "She was very pleased that Only Connect has helped me make such a big change with my life and keep me on the right path."
Asked what Kate thought of the white babygro, which featured the Only Connect logo and the words Prince George underneath, Mr Russell-Andrews said: "She was very pleased about it.
"She said it's a very good fit because he's growing very fast, and that he'll like it.
"Teegan tried to take back the babygro, she's very cheeky.
"Kate said: 'They're very demanding at this age'."
While Teegan was all smiles with Kate, she burst into tears when William started speaking to her father - but she was soon placated with a piece of chocolate cake made by trainees from Switchback, which aims for rehabilitation through catering.
Kate tried two pieces of their cakes herself, one an iced ginger sponge and the other a chocolate cake.
The duchess was wearing a brown Orla Kiely buttoned-down bird-print dress, which she had previously worn on an engagement at The Art Room in Oxford in February 2012, with brown suede ankle boots and brown tights, while William had on a dark blue suit and purple tie.
William's aunt Lady Jane Fellowes, the older sister of Diana, Princess of Wales, is a trustee of Only Connect and described them as carrying out "inspiring and life-changing work" in a recent interview.
A Kensington Palace spokeswoman said it was a coincidence that she is involved however and that the duke and duchess wanted to see the work of the charity as part of their interest in young people, describing it as a "learning and scoping exercise".
Lady Jane spent several minutes in animated conversation with William following the dance performance.
Speaking after their visit, Lady Jane said: "I'm really delighted that William and Catherine have had the opportunity to see the work of Only Connect, a charity that I have been supporting for many years."
William also chatted to dancers Moshood Ibrahim, 20, and Jannick Moth, 22, from Dance United and asked them if there had been a technical glitch - having noticed that music for their modern dance piece only kicked in half-way through.
William said to them: "I could hear clattering going on behind me. So there was a problem?
"I loved how you guys just rolled with it."
Karis Barnard, centre manager at OC Central, spoke to the duchess about programmes the charity runs to help young people, which also reaches out to them through the arts, including poetry.
She said: "She said she wasn't so good at poetry but her photography is her passion. If she's going to do anything artistic, it's that."
During the visit, the royal couple watched workshops being carried out by complementary projects Handmade Alliance, which trains prisoners to produce textiles for British designers, and Bounce Back, which offers training and employment in painting and decorating for offenders at the end of their sentences.
Kate watched volunteers Elise Johnson and Nasser Massadimi making bunting, and said to them: "Are you guys sewing on buttons? It looks very fiddly work."
She added: "It's quite therapeutic, isn't it?"
Danny Kruger, chief executive of Only Connect, which employs 25 people, told William and Kate he was "enormously proud" to welcome them to their headquarters.
Mr Kruger, whose wife Emma founded the charity eight years ago, spoke to them about the importance of charities working together.
After the two-hour visit ended, he said: "It was a great thing to have them giving us a pat on the back and for our members to get congratulated for their work and achievements, and I hope it means we can build our profile and do more work."
Mr Kruger's mother, the presenter, writer and restaurateur Prue Leith, was also present at the Only Connect venue with the royal couple.