I can't answer the question as to the exact dates, however, it's been a succession of events since the beginning of the last century that have led to this point.

I can suggest that the ordering of the pairs is to do with
the sovereignty of the country relative to Great Britain at the time...hence the reason we have pairs like
GBP/USD, AUD/USD, NZD/USD etc...

"Up until World War II, the British pound was the dominant world currency, and the one against which most other currencies were compared. The origin of the pound's nickname "cable" comes from the fact that the U.S. dollar was originally compared against it, and the U.S. dollar and British pound were the first currencies traded by telegraphic cable. The British pound's day as the world's benchmark currency was eroded by Nazi Germany, which launched a massive counterfeiting campaign in World War II which saw confidence in the pound shrink."

"In 1993, the European Monetary System failed when currency traders made a speculative attack on the British pound. As required by the European Monetary System Agreement, the Bank of England intervened to manage the pound's exchange rate. However, the currency market was now so large and so much of the world's currency reserves were in the hands of private traders, that it proved to be too expensive for the Bank of England to manage its exchange rate. The United Kingdom announced its withdrawal from the EMS and the system failed, paving over the final obstacle to the true free-float system we know today."