[Nazaroth]

With 98 Emperors... all saying ruled for about 20 years... give or take... given to some chances of the civil wars mentioned... was about 1960 years of legitimacy of Emperors... by the looks of it they were not always of the same house, as it seems with the many sons and daughters that the 98th one has. (Used as an example.)

As for how this started, probably due to a council of the kings of Britannia (or effectively The British isles)... with one united chief, it would seem that they could hold off the Romans and keep their independence. With this they probably stayed trade partners with the Republic, because the Roman Civil war had yet to happen. So as the kings were united... did Rome stay a Republic? or did did a failing Julius still became murdered within the Senate. In fact... did Caesar still have the fame and glory?

Even with the Empire being thus, a stable trade and dangers of landing and controlling a beach head, probably kept the Britons alive. Given that they would have a stable kinship, probably developed deep partener ship with Rome. Thus when Rome fell, Briton possibly kept a very strong Roman Imperial sense of rule, especially with the offspring constantly trying to win against one another, the smarter and more charismatic would follow through?

As a nexus, or 4th Rome, Londinum (present day London) could have been a support of literary power, A united Briton would be relatively easy to hold against invading barbarians... and without a sword in your back... you can think.
So with the fall of Constainople, and the movement of scientists back into the west... could've sparked a Rennaisance not only in Rome... but in London.

With such it is possible, that wth the beginning of Colonialism and superiority of strategic placement, would've been better off in the arms struggle with Spain and France. With the Neopolianic Wars... maybe Britain would've been far more effective with a constant struggle with its own elites to be the best?

Further still, Even with the Declaration of Independence... maybe the greater power of the elite and constant adaptation ability, would've fared much better in the American theatre, possibly winning the war.

America could've possibly developed much faster, with no regard with the Native Indians due to its deeply rooted beliefs of Ranked society?
Indians as Numbers?

Even with the opening of Japan, it could be seen as a strong example of Britannian as the main opening force... firing of the guns in the port.

With the future control of South america, and Central America, and continue control of India, South Africa and Austrailia... I can easily imagine that Britannia could hold 1/3 of the world's land mass.

Though I believe the World Wars would become null and void, as a tiny Germany would not be able to stand up to the massive industrial and superior manpower that the Britannians could field.

AS for military tactics, they porbably could be found within Britannians favour, due to a constantly competing enviroment... and a wide variety of views which could be found within the Empire.

nuclear development possibly could have been developed... and may have limited the world to one war... Would the depression still exist... it is unknown.

However... this is just what I think. More focus on the Britannian evolution than the other world governments.

(Would Charlemange still be crowned the Emperor of the Romans... I wonder...)

Edit: In support with the council of the british kings... A.T.B... I assume is the timeline frame of reference which stands for (Ascension Throne Britannia) or the beginning of the Imperial line. I know I saw this ATB thing somewhere else... magazine exceprt I believe.

Thus 2017 ATB... given with 1960 years or Britannia hier... 20 years average a piece to each emperor.... it could be seen that the timeline appears to work.