When Telstra announced it would give its mobile customers free data all day on Sunday with no caveats as an apology for last week’s outage, it opened the floodgates.

One industrious user in Sydney spent Sunday tethering his mobile phone to his computer and taking advantage of a 129mbps connection speed to download 421 gigabytes of data, some 7000 per cent of his normal 6GB data plan.

That equated to his entire Steam library of PC games that he synched to his portable harddrive, 25 seasons of educational show How It’s Made and many other different TV shows.

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In a statement, Telstra said Sunday was the busiest day it had ever recorded for its network, with about twice the data traffic of a normal day.

Users downloaded 1841 terabytes of data, the equivalent of about 2.3 million movies or 5.1 million episodes of Game of Thrones, the telco said.

A Sydney Telstra user downloaded 412 gigabytes of data on Sunday’s free data day. Photo: Supplied/ABC

“As soon as midnight ticked over we saw traffic jump up. It reached weekday peak traffic levels by 8:00am and climbed rapidly from there,” Telstra said in a statement.

“Over the course of the day we had twice as much traffic as we would normally see on a Sunday (or any day).”

Some customers complained about their data speeds becoming choked by the network’s heavy traffic while others reported no issues.

After downloading 421GB, the Sydney user told the ABC he was “super happy with the speeds all day”.

“The speeds only got slow and dropped to about 30mbit/s after 10:00pm on Sunday. I guess everyone wanted their last little bit,” he said.

The single day of free data was given to customers after Telstra’s mobile network suffered a mass outage in multiple states last Tuesday.

Telstra’s chief operations officer Kate McKenzie last week said there was a “node malfunction” compounded by “embarrassing human error” that caused the outage.

The data traffic node was taken offline to fix but this resulted in disconnections and heavy congestion on the rest of the network, Telstra said.

– ABC