London Siblings Fighting Over Mother's Will

* 70 year old claims his 65 year old sister and her husband unduly influenced their late mother to rewrite her 2011 will

* He claims they cut him out, leaving him with virtually nothing from the £5 million estate built by their property developer father.

* He accuses the couple of misappropriating £1.685 million from mother's accounts before her death.

A once-close brother and sister now stand as bitter adversaries in London's High Court, locked in a ferocious battle over their late mother's £5 million fortune that has torn apart family bonds and exposed decades of resentment, infidelity, and alleged exploitation.

The dispute centers on Gary MacDougall, a 70-year-old builder who worked alongside his mother Jeanne in the family property business, and his sister Sandra Thomas, 65 reports Daily Mail.

Their father Alec MacDougall amassed wealth through renovating and renting properties in west London's Acton and Ealing areas.

Gary's barrister Harry Martin told Judge Nicola Rushton KC that both parents promised "broadly equal financial treatment and inheritance" for their children.

Under Jeanne's 2008 will, following Alec's death, the estate split roughly evenly: Gary's side receiving properties in Avenue Crescent and Berrymead Gardens, Sandra and husband Philip getting Stuart Road, Avenue Gardens, and most cash.

But a 2011 will dramatically shifted everything — four properties to Sandra and Philip, with Gary and Sandra splitting minimal savings "likely to be worth nil" after administration costs.

Gary alleges undue influence when Jeanne, increasingly dependent and showing signs of diminished capacity, gifted the £1.7 million Avenue Crescent house — previously promised to him — to the Thomases.

He further claims they plundered £1.685 million from her accounts for personal luxuries including Ivy dinners, exotic holidays, vehicles, and a lavish Savoy wedding for their daughter.

Sandra's barrister Alexander Learmonth KC rejected the accusations, insisting no undue influence occurred and Jeanne retained capacity beyond occasional absent-mindedness.

He argued valid reasons drove the changes which included gratitude for Sandra and Philip's caregiving, Gary's relative financial security and possible irritation including his admitted 2008 affair with a local council worker.

Cross-examining Gary, Learmonth pressed:, "Your mother, being of the older generation and being fond of your wife, was not happy with you, was she? She was very disappointed with what you had done."

Gary fired back, "She wasn't happy, no — she was delighted when it concluded. She reminded me of my responsibilities, but it was a very brief fling. If she was cross with me, mum would've let me know. She would've given me both barrels."

He maintained the affair predated the equal 2008 will, proving it did not sway Jeanne, whom he described as "sharp as a tack."

Learmonth countered that Jeanne, from a traditional generation, felt ashamed, supported Gary's wife Anna, and brooded over the betrayal.

The explosive trial continues, with Sandra reportedly admitting she exceeded power of attorney authority on spending but denying deliberate wrongdoing.