A royal rail tour of Britain by Prince William and his wife Kate has caused controversy after criticism from politicians in Scotland and Wales citing coronavirus travel restrictions, reported AFP.

The couple stopped in Cardiff on Tuesday, as part of the 2,000-kilometre tour in the royal train. The purpose of the tour is to thank frontline workers for their efforts during the pandemic.

Before their arrival, Welsh health minister Vaughan Gething told the BBC he would prefer it if "no-one was having unnecessary visits", as per AFP reports. 

He reportedly said he was not "particularly bothered or interested" when asked if William and Kate should travel to Wales, adding that the visit should not be used as an "excuse" for people to say they were "confused" by the current guidelines.

The devolved governments in Wales, Scotland and Northern Ireland are all responsible for their respective health policy, and have consequently implemented different restrictions to curb the spread of COVID-19.

That includes, among others, curbs on all but essential travel between all four UK countries.

First Minister Nicola Sturgeon reportedly said royal officials had been told about restrictions on crossing the border from England. 

"We made sure that the royal household were aware, as you would expect, of all of the restrictions in place in Scotland," she added, as per AFP reports.

The British government in London has refrained from commenting on this matter. Prime Minister Boris Johnson's spokesman said the trip was "obviously a matter for the palace", as per AFP reports.