The security for this week’s visit to Pakistan by the Duke and Duchess of Cambridge is the highest of any royal tour since the Queen’s visit to Ireland.
Prince William and Kate arrived on Monday for their five-day trip to south Asia and it’s "the most complex" one ever undertaken by the couple, according to Kensington Palace.
Unlike Harry and Meghan who took baby Archie on their recent tour in South Africa, the Cambridges won’t be travelling with their children.
William and Kate did take Prince George and Princess Charlotte on a week-long tour to Germany and Poland in 2017 but the security considerations in Pakistan are much greater.
In any event, both George and Charlotte are at school in Battersea, south London.
Prince Louis will be cared for by the family’s nanny.
So why Pakistan?
Its name might mean "Land of the Pure" but there is no doubt this is a country facing some challenges.
Situated with India to its west and Afghanistan and Iran to its East, security and stability are among the main problems facing Pakistan.
As a result, all of the engagements planned for William and Kate’s visit will be kept under wraps until the day of the visit.
But the couple will travel around 700 miles during their tour and they will see the capital, Islamabad, the second biggest city, Lahore, as well as the Himalayas and the more volatile border region in the West.
Kensington Palace called it a "complex security picture" in the region.
Nevertheless, William and Kate will be shown Pakistan’s border region with Afghanistan which is home to a number of fighters loyal to al-Qa’ida.
And there will be some tricky diplomatic moments for the couple to navigate.
Pakistan has been in dispute with its neighbour, India, over the control of Kashmir since the 1940s.
Kashmir is already one of the world’s most heavily militarised regions, and Pakistan’s tensions with its fellow nuclear-armed neighbour heightened in the summer when India imposed new restrictions in Kashmir.
Last month, Pakistan’s Prime Minister, Imran Khan, told the United Nations that India’s actions could provoke war between the two nations – and warned of ‘consequences far beyond the borders’ if that happened between two countries with nuclear weapons.
Prince William confronted similar diplomatic headaches when he visited Israel and the Occupied Palestinian Territories last year.
And the country will also hold some emotional memories for him.
His mother, Princess Diana, was dating a British-Pakistani heart surgeon in the two years before her death.
She came to Pakistan in 1996 to meet Dr Hasnat Khan’s family before the relationship ended, travelling with her friend Jemima Khan, now Goldsmith.
At the time, Goldsmith, was the wife of the cricketer Imran Khan - who is currently Pakistan’s Prime Minister.
The Duke and Duchess of Cambridge have said that they want "the opportunity to meet as many Pakistanis as possible" and the engagements will involve school children, sports stars, cultural figures as well as politicians.
With 207 million people, Pakistan is one of the most populated in the world (about the same number as Brazil and a little more than Nigeria) and 96 per cent of them are Muslim.
But the people are not wealthy.
As measured by GDP per head – Pakistan is in the bottom quarter of the world tables.
William and Kate will also use the visit to draw attention to the effects of climate change and how communities are ‘rapidly responding’ to those effects.
During his stay in Botswana and Malawi last month, William’s brother, Prince Harry, highlighted similar concerns and spoke of how humans are to blame.
As ever, Royal Tours are conducted "at the request of the Foreign Office" - and given Pakistanis are the single largest minority ethnic group in the UK, the government is hoping the visit will strengthen what diplomats call the ‘people to people’ ties between countries.
William and Kate return to the UK at the end of the week.