Princess Diana’s brother Earl Spencer has been caught in the middle of an explosive High Court battle between his new lover and his estranged wife.

Professor Catrine Jarman, Earl Spencer’s archaeologist girlfriend, is suing Countess Karen Spencer for allegedly revealing intimate secrets about her which has caused her ‘distress and embarrassment’.

Earl Spencer, 60, and Dr Jarman, 42, confirmed their romance in October – after he announced his split from Lady Spencer, 52, in March.

But his old and new lovers are now set to clash in a bitter High Court showdown over the spilling of intimate secrets.

Viking expert Dr Jarman has accused Lady Spencer of revealing private details of her life to close friends, sparking a major rift at the heart of one of Britain’s most famous families.

Dr Jarman, who grew closer to Earl Spencer after a dig at his ancestral home where he grew up with his late sister Diana, claims the leak in May caused her ‘distress, upset and embarrassment’.

The Mail revealed in October that Dr Jarman was taking Lady Spencer to court over ‘misuse of private information’.

The paperwork, as reported by The Sun last night, says: ‘Dr Jarman was unaware until around mid-May that the Countess had even obtained the private information.

‘She only found out after the Countess had disclosed the information to Earl Spencer — the revelation of which was shocking to her.

‘Dr Jarman did not, at any time, provide her consent to the Countess to disclose that information to any third party or intimate anything to that effect.’

It goes on to say the lack of consent should have been ‘obvious’ to the Countess given the nature of the information. She has accused the Countess of spilling the secrets to  a ‘close group of personal friends’.

The Countess is accused of telling those involved in bringing up their 11-year-old daughter, Lady Charlotte Diana.

The list also reportedly includes teachers and parents at Spratton Hall School, an £18,600-a-year private school in Northants.

It is claimed that the Countess even told her personal trainer.

Dr Jarman is seeking damages and an injunction banning Lady Spencer from telling others and a full list of those already told.

She says the Countess is liable to the damage she has allegedly caused.

Details of the High Court showdown have emerged just a week after Countess Spencer revealed she’s going through a ‘challenging time’ as she moves home amid her divorce.

Lady Spencer, who is leaving Althorp House, located in Northampton, admitted that it has not been an easy transition.

The Earl and the Countess announced their split back in June – with Lady Spencer set to move out of her ex’s estate after 14 years. Althorp House is where Earl Spencer and his late sister Princess Diana grew up.

Lady Spencer took to Instagram last week and wrote: ‘It hasn’t been easy finding a temporary rental that can accommodate seven horses, two sheep, four cats, and a dog – but with the help of some wonderful friends, we’ve finally found one.

‘It’s been a challenging time, but also one filled with so much generosity and kindness. No exact move-in date yet, but we’re getting close.’

It comes after Earl Spencer confirmed his relationship with Dr Jarman in October.

Speaking on Good Morning Britain, he opened up about his relationship with the Scandinavian archaeologist and podcast star for the first time.

Gushing about his new girlfriend, he said: ‘Cat Jarman, who is my partner now actually, she’s a brilliant archaeologist.

‘She is Nordic Person of the Year 2024 which is usually handed out to someone like Sven-Goran Eriksson or a composer or something. You have to be respected throughout all Scandinavian and Nordic countries.’

Dr Jarman, who is separated from her husband, has been helping Earl Spencer unearth a Roman villa in Althorp.

Since 2023, Earl Spencer and Dr Jarman have co-hosted The Rabbit Hole Detective, which is a historical podcast, alongside Reverend Richard Coles.

Lady Spencer, Dr Jarman and Earl Spencer have been approached for comment.