Harry and Meghan drive themselves around California with Doria after recording Oprah interview

Prince Harry and Meghan Markle are set to appear in one of the most explosive and highly-anticipated interviews in royal history this weekend - and it looks as though the pressure of their no-holds-barred sit-down with Oprah Winfrey may well be causing some tension.

The couple were seen looking very somber while driving around Santa Barbara with the Duchess' mother Doria on Sunday afternoon - hours before two teaser clips from their no-holds-barred primetime interview were shared, sending tremors through the palace by laying bare just a few of the sensitive, and potentially-uncomfortable topics discussed by the Sussexes.

In exclusive images obtained by DailyMail.com, Prince Harry, 36, is seen behind the wheel of the couple's Range Rover while driving his 39-year-old wife and 64-year-old mother-in-law near their $14.5 million home in Montecito.

The couple appeared incredibly somber while out for an afternoon drive with Doria, who was sitting behind her daughter and remained partially-hidden from the camera.

It may well be that the Sussexes were feeling apprehensive about the release of the trailers for their sit-down interview with Oprah, which is expected to cover a number of controversial and private topics, from Meghan's experience of royal life and the couple's exit from royal duties, to their much-publicized rift with Harry's family at home.

When the interview was first announced last month, the news sent tremors through Buckingham Palace - with experts and insiders warning the royal family to 'hide behind the sofa' when it is broadcast over fears of what might be said by the couple about their treatment from Harry's family and palace officials.

Royal experts said Buckingham Palace should be 'scared' about the 'wide-ranging' interview, particularly after it was revealed that the primetime sit-down had been extended from 90 minutes to two hours - perhaps to give the couple an opportunity to address the finalizing of Megxit, which took place one day after the shoot initially wrapped.

But with Harry's grandfather Prince Philip, 99, transferred to St Bartholomew's Hospital in London for 'testing and observation for a pre-existing heart condition' following a two-week stay at King Edward VII Hospital last night, some fans and royal experts have suggested the Sussexes ask CBS to postpone the broadcast of their bombshell interview.

Doria reportedly moved in with Harry and Meghan last summer in order to help them care for their son Archie - and her presence is no doubt all the more essential now that the Sussexes are preparing to welcome their second child later this year.

However it seems not even Doria - who Meghan is known to be very close with - could raise a smile from the couple, who remained straight-faced while out for their Sunday afternoon drive.

As part of their permanent stepping down as senior working members of the royal family, Harry and Meghan were both stripped of their existing patronages and honorary titles - a move that is set to have 'upset' the couple, who took a swipe at the palace in an unprecedented statement in which they insisted 'service is universal'.

The extra half-hour of the show will allow CBS to rake in more lucrative advertising, with a 30-second primetime slot believed to cost around $200,000. According to Page Six, the Sussexes are not being paid for the Oprah interview, but experts believe it is part of their ongoing plan to build a billion-dollar brand in the US.

In one of the teasers, Oprah, 67, is seen probing Meghan about whether she was 'silenced' by the Queen and the palace - an assertion that sparked outrage among royal insiders, who said it was 'ridiculous' and 'unfair' to paint the monarch as some kind of mob boss like Don Corleone from The Godfather.

Meghan says nothing as Oprah questions whether she 'was silent or silenced', and simply nods her head while cradling her blossoming baby bump, which she highlighted in a $4,700 Armani dress that was belted above her growing stomach.

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