Meghan Markle seen wearing anti-stress wrist patch during shopping trip

The Duchess was attending an appointment in the Sussexes’ hometown of Montecito, California when she was seen with the accessory.

Each daily "biosignal processing disc" by NuCalm costs £3.15 which, if worn every day, would cost around £1,150 a year.

The patches send a signal to the heart, slowing down cellular actions to mimic the “body’s normal transition to a peaceful, restorative night’s sleep”.

NuCalm states that it does this by “activating the parasympathetic nervous system” with electromagnetic frequencies.

With Prince Harry currently away in Asia, Meghan was also spotted alone wearing a Max Mara Ruspoli jacket worth $1,625 (£1,280) and a Hermès Rayures D’Ete shawl that costs $1,225 (£965).

NuCalm confirmed it was a bio-signalling disk seen on her left wrist.

Using the paparazzi picture on their story, they wrote: "Yes, that's the NuCalm bio-signalling disc, a tool to get most clinical benefit from your NuCalm subscription."

Users of the patch are instructed to wear only on their left wrist and to place it three-finger lengths away from the wrist.

It comes after Prince Harry travelled alone to Asia for the polo match with professional player and friend Nacho Figueras.

The Duke of Sussex played in the Sentebale ISPS Handa Polo Cup at Singapore Polo Club on Saturday, a sporting event he set up which aims to raise money for children affected by poverty, inequality and HIV/AIDS.

His best friend and polo opposite number Figueras told reporters: “We miss our wives very much.

"This was a very short trip, although it’s a few days, it’s a lot of travelling for 24 hours in Japan and a few hours here, but we miss them. We wish they were here.”

The Argenitian polo professional added that it had been lovely to catch up with Harry: “Being able to spend so much time together has been a wonderful thing.”