It will be the fourth time a Japanese city has hosted an Olympic Games and on every previous occasion, organisers have paid particular attention to the symbolic meaning of the Flame.

Back in 1964, the giant cauldron was lit by Yoshinori Sakai, a boy born on the day the atom bomb was dropped on Hiroshima in 1945.

In fact, Tokyo had been invited to host the 1940 Olympics and Winter Olympics. War, first in China and then with the Western Allies, made this impossible.

Germany and Japan were both excluded from the 1948 Olympic Games. In those days, invitations did not come directly from the International Olympic Committee (IOC) but from the local Organising Committee. 

At the time, feeling towards Japan was particularly bitter. American runner Louis Zamperini had competed in the 5,000m at the 1936 Olympics. He was among many prisoners of war to receive brutal treatment from their Japanese captors. His experiences were recounted in Angelina Jolie’s 2014 film, "Unbroken".

In June 1948, as the London Olympics approached, alarm bells began to ring as there was talk that a group of Japanese officials wished to visit the Games. Organising Committee chairman Lord Burghley wrote at once to IOC President Sigfrid Edström in Stockholm.

"We have been shocked to receive your letter concerning the Japanese members of the IOC coming here for the Games," he wrote.

"There would be a public outcry if they were present, which would probably lead to the withdrawal of some of the dominion teams who feel most strongly on this question.

"I feel it is as well that I should be frank with you from a personal angle. We have no peace treaty with Japan and it would obviously be quite impossible for the king to meet them at the Opening Ceremony, or any of the official guests at the dinners."

It was customary for the head of state to meet IOC members in a very public ceremony on the field at the Opening Ceremony.

Burghley signed off by asking Edström to tell the Japanese that "their presence on this occasion is quite unacceptable".

A former Governor of Bermuda, Burghley had used his own contacts in diplomatic channels to seek advice.

"We consider that the presence of the Japanese would cause serious public resentment here and would precipitate a first-class row with the Australian and New Zealanders whose views on the subject of Japanese leaving Japan are well known to you," came the response.

Sir Arthur Porritt, an IOC member in New Zealand, made it clear he would refuse to meet any Japanese members.

Burghley was advised to tell the IOC that "Japanese subjects are not allowed to leave the country except by permission of the Supreme Commander for the Allied Powers and this is normally confined to occasions when their journeys are necessary for the purpose of the occupation".

It was made clear that an Olympic visit would not be considered sufficient reason for permission to be granted.

"Unfortunately, the Japanese are suffering from intensely swollen heads by reason of the ever-increasing relaxation of the ban prohibiting them from travelling abroad," said an inter-departmental memo from the British Embassy.

It described those who made the request as "certain hot heads". The reaction from British officials was to have "immediately thrown the coldest water possible on this suggestion".

"We hope we shall hear no more of this proposal. The Supreme Allied Commander must be aware that it would be embarrassing and unwelcome, not only to us but to many of the other competing countries."

Edström’s reply to fellow his IOC member Burghley was surprisingly blunt.

"I am surprised you take this attitude three years after the war. We men of sport ought to show the way for the diplomats. Besides, many Germans in official positions have visited Britain."

Sweden had maintained neutrality during the war.

Despite the wishes of the IOC President, the Japanese were not seen in London. They had to wait until 1951 when the first Asian Games were held in Delhi to compete again in an international Games, but after that they were rapidly reintegrated.

In 1958, they staged the IOC Session and the Asian Games. Both were considered successes and the following year, they were elected 1964 host city.

At first they planned for a grand Torch Relay along the great Silk Road but the official report recorded "numerous difficulties presented made this impracticable".

Instead, the Flame was flown to Japan with stopovers en route. It was carried by polo players in Tehran, serenaded by bagpipes in Lahore and even a typhoon in Hong Kong could not prevent its progress.

In Japan, a visit to the peace monument at Kagoshima was highly symbolic. The Flame was also taken to Hiroshima. It had divided to allow as many as possible to see it and was reunited on the eve of the Opening Ceremony.

The identity of the final runner, Sakai, had been made known in advance.

"Happily, I know nothing of war. I have grown up free from care in the atmosphere of freedom in a peace-loving Japan," he said.

"People all over the world paid a great deal of attention to who would be chosen for this important role," said his coach Teruji Kojake, recalling the events during Tokyo’s bid for the 2016 Games.

‘’It was difficult to fend off the mass media who were determined to find out who it was. As a coach, I was tailed by reporters. 

"Sakai had come to Tokyo from Hiroshima and when it became impossible to have him stay at my house, I put him up at a hotel and gave him advice and guidance there.

‘’On the morning of the long-awaited opening day, we celebrated at my home by eating festive red rice that my wife had prepared and sent him off with prayers for success."

Five men and two women carried the Flame from the Imperial Palace Plaza to the stadium where in the words of the official report, "a roar of excitement greeted this youthful runner".

Sakai described his selection as "proof of the high hopes that Japan places in the younger generation".

In the stands, living every moment, was Kojake.

"I watched tensely. To this day, I clearly remember the sense of relief I felt when I saw him perform his role splendidly," said Kojake.

Sakai went on to win relay gold at the 1966 Asian Games before pursuing a career in television. He died in 2015.

The new year heralded the arrival of the Flame on the Japanese mainland for the 1972 Sapporo Winter Olympics. It had spent the previous night in Okinawa where "the excitement displayed towards the Olympic Movement was truly wonderful".

Organisers said "it was possible to conceive of a richly-variegated relay on skis, skates, horseback or sledge depending on the characteristics of each region".

When the Flame arrived in the stadium, it was carried symbolically by both men and women. Sixteen-year-old skater Izumi Tsujimura carried the Flame to the foot of a stairway where the final bearer was Hideki Takada, another teenager.

"Having received the Torch, the youthful athlete bounded up the 103 steps and after raising the Torch high in a final salute, he ignited the Flame."

The 1998 Nagano Games came in the wake of a fierce conflict in the Balkans.

Chris Moon, chosen to represent the Landmine Survivors Network, carried the Flame into the stadium. A former soldier, he had lost an arm and a leg whilst attempting to defuse a mine. As he ran, 150 children dressed in the colours of flags of the world ran in alongside him. The music was Andrew Lloyd Webber’s "When Children Rule the World".

Ceremony producer Keito Asari explained: "Japan is responsible for the curse of wars in the first half of the century. Chris Moon represents the sadness of the past century and the children represent the hope for the next century."

A few days earlier, Zamperini, the former prisoner of war, had accepted an invitation to carry the Flame.He did so in Naoetsu, not far from where where he had been imprisoned during the Second World War.

"It was a thrill, I’d never seen such enthusiasm in a Torch Relay," he said at the time.

At the Opening Ceremony, IOC President Juan Antonio Samaranch had spoken of a desire to "foster international dialogue in an effort to bring human tragedies to an end".

In a moment of poignant symbolism, the 2020 Flame will be kindled in Ancient Olympia on the day the tsunami struck in 2011.

When it arrives on Japanese soil, it will visit the Ishinomaki Minamihama Tsunami Recovery Memorial Park and journey to Fukushima in what is described as a "display of the Flame of recovery".

The itinerary will also feature the Hiroshima Peace Memorial Park.

The journey of the Flame is always emotional for those who see it pass by. It will be equally poignant when the Flame is extinguished, because the Closing Ceremony falls on the 75th anniversary of the day the atom bomb fell on Nagasaki.