After history was made in front of Japan’s media who gathered to witness the event, Field Army Commander, Lieutenant General Patrick Sanders told me how significant a moment it was: "This is a small exercise but this is a big deal for both countries.
"It's important to Japanese security, it's important to Britain's role as a global power and our future as we change our relationship with Europe - this matters."
Lance Sergeant Liam Magee, Honourable Artillery Company, said he had already built up a rapport with his Japanese counterparts and it’s not all to do with soldiering: "The Japanese have been on an exercise in Wales that we've run before and they were just commenting on some of the English diet.
"I think they've been subjected to the traditional English fried breakfast every morning to which beans were their favourite part!
"There's always a commonality with soldiers - equipment, interest in each other's weapons, each other's rations so I think that always gives any soldier a basis for a discussion - a common point."
Tokyo in 2018 is a bustling city - the capital of the world’s third largest economy. Japan has recently reported the longest period of economic growth in more than two decades. Yet scroll back in time and things couldn’t have been more different.
1945 - a moment the world stopped twice, as thousands upon thousands were killed as two atomic bombs were dropped on Hiroshima and Nagasaki. An end to the War that took so much from so many.
When World War Two ended, a new pacifist constitution was announced by Emperor Hirohito. Article 9 of the document said that Japan forever renounces war and forbids the use of force to settle international disputes.
Video: A look at Japan's recent military history.
But in 2018 the country’s Prime Minister Shinzo Abe is pushing for a change to formally recognise Japan’s military in the constitution, clearing up any question marks over its legitimacy.
Today Japan's Self Defence Forces total nearly a 247,150 active personnel, dwarfing the UK’s which is more than 150,000.
But compare that to the countries causing Japan the most security concerns North Korea has 1,280,00 active personnel, China has 2,035,000, and Russia has 900,000.
In 2017, relations between Japan and North Korea reached an all-time low after one of Pyongyang’s intercontinental ballistic missiles landed in Japanese waters.
Mr Abe described it as a “reckless act” representing an unprecedented serious threat.
Since his re-election, defence spending has increased and he’s trying to push through the changes he wants to the constitution.
On the streets of Tokyo, the local people I spoke to were divided on the subject. I met Keiko, a 62-year- old retired pharmacist, who doesn’t think the constitution should be changed.
She said: "We have to run from that history" adding that if the constitution is changed Japan risks repeating history.
But Mayu, a web designer in her late 20s, said it was "great" to see Japan working with the UK.
On a visit to Japan last year, UK Prime Minister Theresa May laid the groundwork for a 3-year defence cooperation plan which is what’s led to the the UK-Japanese joint exercise.
Video: British Ambassador to Japan speaking to Forces News.
Prior to watching the exercise himself, the British Ambassador to Japan exclusively told Forces News at the British Embassy in Tokyo that the exercise was "significant for two reasons".
Paul Madden explained: "Firstly, it's a very concrete manifestation of the closer, enhanced security relationship that we have with Japan, following the Prime Minister's visit to Tokyo last year when she and Prime Minister Abe set out a new vision for our relationship," he explained.
"Secondly, I think it's important because it's the first time anyone other than the Americans has been doing land-based exercises with the Japanese on Japanese soil.
"I think for Japan, it's very welcome to have countries like Britain doing more with it because it's a time of uncertainty in the region, so Japan is looking to have closer relationships with those countries that share its values."
Mr Madden added:
"I expect to see an overall general strengthening of the relationship."
The troops will now head north to Sendai for week two of Exercise Vigilant Isles.
Once the Exercise has concluded, the focus will then be to build on the historic foundations that have been forged here in Fuji.