LONDON (Reuters) - Emperor Naruhito and his wife begin a week long visit to Britain on Saturday, visiting Oxford University where they both studied and attending a formal banquet with King Charles, but there are no plans for a meeting with Prime Minister Rishi Sunak.

Naruhito and his wife, Empress Masako, had been due to make the trip in 2020 when Queen Elizabeth was still alive but it was postponed because of the COVID-19 pandemic.

Their first overseas trip together after his enthronement was to Elizabeth's funeral in 2022, and ahead of the state visit Naruhito, 64, spoke of the kindness the British royals had shown to him when he arrived in Britain to study in the early 1980s.

He recalled how the late queen had invited him to Buckingham Palace for tea which she made herself.

"I have fond memories of the heartwarming hospitality I received from her majesty the queen and the royal family, making me feel like I was part of their family," he told a news conference held in Tokyo.

The emperor's trip is the third state visit of Charles' reign, but the first since it was revealed earlier this year that he had been diagnosed with cancer.

Naruhito said he was grateful the king would host them despite his illness, and he also sent good wishes to Charles' daughter-in-law Kate, wife of heir Prince William, who is having preventative chemotherapy treatment for cancer.

"I understand that they are both going through a hard time, but I pray that their treatment will go smoothly and that they will have a speedy recovery," he said.

The official reason for the trip is to celebrate the long ties between the two royal families, and to demonstrate the deep relationship between the two countries.

However, the Japanese royals are also using it as a chance to return to Oxford where they both studied at separate times, while Naruhito will visit the River Thames flood barrier which he had researched while at university there.

The visit clashes with campaigning for the British election on July 4, and a Japanese foreign ministry official said there were no plans for a meeting with the prime minister.

The official state elements of the trip begin on Tuesday when Prince William will formally greet the emperor, before a grand carriage procession along The Mall to Buckingham Palace where there will be a state banquet.

During the trip Naruhito will also privately visit St George's Chapel at Windsor Castle to lay a wreath on the tomb of Queen Elizabeth.

(Reporting by Michael Holden and Sakura Murakami in Tokyo; editing by Miral Fahmy)