William and Kate are joined by reindeer for royal train tour

The Duke and Duchess of Cambridge have surprised schoolchildren with a visit from reindeer during a three-day train tour of Great Britain.

Kensington Palace arranged for Chaz, Crackers and her calf, Echols, to join the couple at a school in Berwick.

Prince William and Catherine are travelling around Great Britain to thank key workers for their efforts during the pandemic.

Their first stop was Edinburgh, where they met frontline ambulance workers.

The duke and duchess had travelled to Scotland overnight from London's Euston station.

The 1,250 mile tour on board the royal train will include stops in England, Scotland and Wales.

The couple, known as the Earl and Countess of Strathearn in Scotland, arrived at Edinburgh Waverley station on Monday morning to the sounds of a piper playing Christmas songs including Jingle Bells and Santa Claus is Coming to Town.

Their first official engagement saw them visit the Scottish Ambulance Service in Newbridge, near Edinburgh, where they met front-line staff.

They heard moving accounts from ambulance workers about how they have been personally affected by the crisis.

Paramedic Alistair Matson told them about how he had to cope with his father falling ill and later dying in hospital during the pandemic.

Mr Matson, 54, said: "It was very emotional talking to the prince about losing my father. He was very anxious to hear how we managed to cope with the mental strains of our job."

The visit coincided with the announcement that the couple have become joint patrons of NHS Charities Together.

Ian Lush, chairman of NHS Charities Together, said it was "such an honour for our organisation", adding that their involvement will inspire the public "to do even more to support the amazing NHS staff and volunteers".

Earlier this year, Captain Sir Tom Moore raised more than £33m for NHS Charities Together by walking 100 laps of his Bedfordshire garden before his 100th birthday.

Later asked whether the visit to Scotland broke coronavirus rules banning cross-border travel, Scottish First Minister Nicola Sturgeon said the royal household was made aware of the restrictions ahead of time.

Royal sources said the Cambridges' trip was planned in conjunction with the UK, Scottish and Welsh governments and that travelling across the border is permitted for work purposes.

The royal couple then crossed the border to visit Holy Trinity First School in England's most northern town, Berwick-upon-Tweed.

The school's 175 pupils waved and sang as the duke and duchess arrived, while local saxophone group The Earl Grey Saxes played Christmas tunes, including Rudolph the Red Nosed Reindeer.

As a surprise for the children, Kensington Palace had organised for Rent a Reindeer to bring three animals to the school.

Rent a Reindeer owner George Richardson said the booking by the palace had been "top secret".

He said: "We got a phone call out of the blue two weeks ago, they asked us to bring a reindeer for the royal visit and we were happy to oblige.

"This was baby's first outing and she took it in her stride," he added, talking about the calf.

Headteacher Nicholas Shaw said the school felt "honoured" to have been chosen for the royal visit, adding: "We appreciate they are taking the time to think about teachers and the work that has been going on in schools."

The royals went on to Batley Community Centre in West Yorkshire and met volunteers from the centre who have supported elderly members of the community throughout the pandemic.

They also met Len Gardner, a local resident with whom the duchess has been chatting on the phone after she secretly volunteered through the NHS Volunteer Responder Check In And Chat scheme.

Their final stop on Monday was in Greater Manchester, where they visited the FareShare charity, which redistributes surplus food from businesses to 11,000 charities and community groups across the UK.

Before leaving London on Sunday night, the duke and duchess left a personal message of thanks for transport workers on a London Underground service information board.

Kensington Palace shared images of Catherine writing the notice, which read: "Thank you to all transport workers everywhere for keeping the country moving throughout this difficult year.

"Wishing you all a very Merry Christmas!"

They were also serenaded by singer Shakin' Stevens, who performed his hit festive song, Merry Christmas Everyone, at the station.

The royal tour, which ends on Tuesday, will see the couple meet care home staff, teachers, pupils and volunteers to learn about the challenges they have faced during the coronavirus pandemic.