Prince Harry and Meghan's tell-all Oprah interview was 3 years in the making

The couple is set for a sit-down interview with Oprah. Photo / Supplied

TV icon Oprah Winfrey courted Prince Harry and Meghan Markle for three years before landing the exclusive tell-all interview with the couple, according to reports.

The 67-year-old talk show queen is no stranger to the couple, however, she only met Markle once before attending the couple's wedding in 2018 when she was reportedly trying to land an interview, according to the Times of London.

The host played what the UK Times referred to as the "long game" acting as a mentor to the Duchess and befriending her mother Doria Ragland when the couple moved to Winfrey's upscale California neighbourhood last year.

Winfrey's series about mental health for Apple TV with Harry was seen by many royal insiders as a "canny move" to "keep the couple happy", the report said.

Winfrey landing the exclusive interview was long an "open secret in palace circles" — with Page Six noting speculation about it last January.

However, when the announcement came it still reportedly caught the palace by surprise, with royal officials only learning about the finalised interview on Twitter on Monday, the report said.

Oprah Winfrey arrives at St George's Chapel at Windsor Castle before the wedding of Prince Harry to Meghan Markle. Photo / Getty Images

The interview will air on March 7, a week after the end of the one-year trial period for the Sussexes' split from royal duties. The UK Times notes the timing may only widen the rift between the couple and the rest of the royal family in the UK.

The royal family, however, has a disastrous history with tell-all TV interviews, including Harry's late mother Diana who went on to regret the infamous 1995 Panorama interview.

Diana opened up about her self-harm, bulimia and infidelity in her marriage to Prince Charles, famously saying "there were three of us in this marriage, so it was a bit crowded".

In recent years, Prince Andrew agreed to a BBC interview about his relationship with paedophile Jeffrey Epstein. Andrew faced severe backlash and was officially stood down from royal duties.