The robbery happened in North End Road , with police called to the scene at 12.38pm.
By the time officers arrived the suspect had fled with a quantity of goods and cash.
No one was hurt, police confirmed.
Speaking on Wednesday (September 27), Carphone Warehouse said in a statement: “The safety and wellbeing of all our staff and customers is our utmost priority.
“The investigation into this incident is ongoing and anyone with any further information should contact the local police.”
The Met said officers from its Trojan unit attended.
One witness spoke of seeing a heavy police presence close to the West Kensington Estate near Fulham Boys School, with five police cars with officers wearing body armour in attendance.
Another witness reported seeing armed police unit “flying down Walham Grove” at around 4pm or 5pm.
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