The phrase "arguably once" is correct and usable in written English.
It can be used when discussing a point that is open to debate or interpretation, particularly in reference to a past event or state.
Example: "The city was arguably once the cultural capital of the region, attracting artists and thinkers from all over."
Alternatives: "possibly at one time" or "debatably in the past".
In fact, all were, arguably, once bright and artistic.
Indeed, while religious freedom as a political idea was arguably once a force for tolerance, it has now become a force for intolerance, she maintains.
Constantinople: City of the World's Desire, 1453-1924, by Philip Mansel John Murrayy, £10.99) Starting with a triumphant arrival into the sacked city by its Ottoman conquerer, Sultan Mehmed II, this is less a history than a detailed 'biography' of what was arguably once the world's greatest city.
Rene Reinsberg, VP of Emerging Products at GoDaddy, explained that the goal is to allow entrepreneurs to get feedback on businesses at the idea stage, since nowadays most crowdfunding campaigns (which were arguably once supposed to be built just around ideas) require a lot of upfront polish and capital.
Online, the title accuses Joachim Löw's team – once arguably the most exciting in the world – of "slow-motion football".
Vermont, Hawaii, and, arguably, California were once independent republics, too, but they don't make a fetish of it.
NBC, once arguably the biggest cultural tastemaker in the United States, is being shopped to Comcast, the country's largest cable company.
"It is clear," said the mild-mannered Mr Murphy, "the city needs a fresh start".San Diego, once arguably America's best-run big city, is now better known for its collapsing credit ratings and talk of bankruptcy.
The nostalgia: the New York Times Magazine was once, arguably, the most influential magazine in America (the runner ups would be the New Yorker and Time), as well as one of the most profitable.
Once arguably the most powerful man in the world, he now works to pave local basketball courts or persuade an auto shop not to clutter up the town's historic sights.
These leafy Victorian streets were once arguably some of the city's loveliest, and outside many of the small terraced homes today there are tubs of runner beans, tomatoes and sweetcorn.
