The Duke and Duchess of Cambridge will travel to Warsaw with Prince George and Princess Charlotte for the start of their five-day tour of Poland and Germany.
William and Kate's trip, taken at the request of the Foreign and Commonwealth Office, is likely to be seen as another Brexit diplomacy tour, helping to maintain and strengthen the UK's relations with Europe as it leaves the EU.
But all eyes will be on the couple's children, George aged three and two-year-old Charlotte, who are getting used to travelling overseas having joined their parents in Canada last year for an official trip.
They are likely to be seen on only a few occasions during the tour of Poland and Germany, making appearances during arrivals and departures at the two countries, and possibly at one or two of the engagements.
Royal watchers will also get a glimpse of Kate's new haircut dubbed the "Kob", Kate bob, which she debuted during a visit to Wimbledon last week.
Kate appears to have lost quite a few inches from her tresses and it has a vibrant deep brown colour.
A Kensington Palace spokesman has said: ''The Duke and Duchess are very much looking forward to this tour and are delighted with the exciting and varied programme that has been put together for it.
''They have decided that their children, Prince George and Princess Charlotte, will travel with them and we expect the children to be seen on at least a couple of occasions over the course of the week."
William and Kate's five-day trip will begin with a welcome from President Andrzej Duda in the Polish capital, followed by a visit to the Warsaw Rising Museum, dedicated to the 1944 Polish uprising to liberate Warsaw from German occupation during the Second World War, and end with a Queen's birthday garden party.
During their five-day tour William and Kate will also meet survivors of the Holocaust and Nazi oppression as they acknowledge the complex 20th century histories of each country.
In Poland, they will tour the former Stutthof concentration camp where 65,000 people died at the hands of their captors, and also visit Berlin's Holocaust museum and memorial.
They will also tour the site of Gdansk's shipyards, the birthplace of Poland's Solidarity movement that helped topple Communist rule.
Here they will meet with founding members of the organisation but it is not known if Lech Walesa, Poland's former president and leader of its peaceful pro-democracy struggle, will be present.
Chancellor Angela Merkel will hold a private meeting with the royal couple in Berlin at the start of the German leg of their tour on Wednesday, and afterwards William and Kate will visit the Brandenburg Gate, a symbol of German unification.
The mood will change when the duke and duchess renew their friendly sporting rivalry, that seems to play a part in most of their trips, when they visit the picturesque Germany city of Heidelberg, twinned with Cambridge.
William and Kate will take to the waters of the River Neckar to cox opposing rowing teams in a race with crews from drawn from Cambridge and Heidelberg.