It is believed the coffee chain is rolling out the special offer across the UK for two weeks beginning in April.
The offer is currently available at the Canary Wharf branch of the coffee chain, with more stores across expected to follow suit.
A banner advertising the offer was placed outside the London chain, which reads: "Freshly brewed, enjoy a tall filter coffee for £1."
In a bid to find out why the coffee mega brand are trailing the cut price drink, we spoke to one of the employees about the deal.
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The offer comes after Starbucks announced it will trial a 50p discount to people who bring their own cups.
In a bid to beat waste, customers who bring their own mugs will receive a discount on all drinks.
PAStarbucks takeaway cups. There are "shocking" amounts of sugar found in a number of hot drinks regularly bought on Britain's high streetsIt is believed Starbucks are offering £1 filter coffees for a limited time only
A Starbucks spokesperson said: "In the UK we offer a 25p discount if you bring in your own reusable cup to our stores.
"From 1st April for two months, we’ll be trialling an increase in the discount of our reusable cup incentive to 50p for every drink purchased in any reusable cup, with the single exception of our £1 filter coffee.
READ MORE: Drink MORE coffee to reduce your risk of developing multiple sclerosis, experts say
"This can be any reusable cup, not only a Starbucks one – which we sell from £1.’
It is thought the trial may pave the way for a permanent discount to help reduce the number of paper cups being dumped at landfill sites.
With more than 2.5 billion paper cups dumped across Britain, the scheme is being hailed as a victory for waste activists.
Starbucks are trialling £1 filter coffees and could be a permanent feature on their menu
