The fitness freak Duchess of Sussex thought it would be a “no brainer” for her to participate in the iconic race as her efforts would have raised millions of dollars for global good causes.
But it has been decided behind the scenes it would be “unseemly” for a senior royal to be seen sweating in skimpy running gear along the 26-mile course.
Yet Meghan, 36, has been lied to by royal aides who told her security fears are behind the block on her participating.
A source close to the former actress said she knows the security scare is “rubbish” as she is “painfully aware” veteran royals are keen for the clan to maintain an air of “aloof untouchability” in public.
Meghan’s marathon ban is the latest blow for the brunette, who used to blog about sex and revel in filming sex scenes when she was in TV show Suits.
She is reeling from her dad’s latest public outburst on how their relationship has been shattered by her marriage to Prince Harry 10 weeks ago.
Top-level royal advisors are holding crisis talks after Thomas Markle Snr, 74, babbled in an interview over the weekend about how his daughter is being stifled in the same way as Princess Diana was suffocated by the royal family – eventually driving her to the brink of insanity!
A source close to Meghan said: “Meghan values her freedom above everything else, and she was hoping being able to participate in the London marathon would show the world she is her own woman who does not have to take orders from the royal family.
“She was especially intent on doing it after her father embarrassed her again by saying she is being trapped and ordered around by the royals in the same way Diana was.
“But Meghan has been told in no uncertain terms there is no chance in hell she will be able to run in next year’s London marathon.
“She has been told it is because of security – but knows the real reason is because royal protocol dictates that it is unseemly for senior royals to be seeing sweating away in workout gear with a public mob.”
Meghan fought to overturn the decision to bar her from the race by suggesting a security detail could run alongside her.
Our insider revealed she also suggested running only part of the course in a special lane to raise money for causes close to her heart, such as World Vision, the planet’s largest children’s charity.
They added: “Any suggestion Meghan made was rebuffed and it was insisted the reason she couldn’t take part in the marathon was fears she is a kidnap and terror target.
“However, she knows it’s rubbish as the royals regularly cheer on the racers and it is one of the most closely monitored events in the UK by the police.
“She’s also disappointed she couldn’t use the run to raise money for charity as she had plans to announce her participation online and urge people to give to causes such as World Vision.
“Her online following means she could potentially have raised millions.”
They had wanted to join the marathon last year to raise cash for the mental health charity Heads Together championed by William and Harry.
But our source said security is only one of the reasons they were barred – adding the Queen hated the idea of seeing her family “huffing and puffing” through the race with 40,000-plus runners.
It comes after we reported earlier this year how Meghan had a secret entrance fitted to her favourite yoga class in London so she would not be seen in public in her clingy Lycra gear.
Meghan’s marathon ban fury is the latest sign she is struggling to deal with the old-fashioned ways of the royals – ominously dubbed ‘The Firm’ after their uncompromising imposition of restrictive rules.
RadarOnline.com can also exclusively reveal she is raging her entire wardrobe collection had to be altered with weights to ensure her clothes don’t blow in the wind and reveal too much flesh to the public.
The former actress’ tops and dresses have had weights sewn into the lining to avoid the hems, sleeves and necklines from showing the upper parts of her thighs, arms and cleavage.
And Meghan is also said to be growing “frustrated” with having to check her outfits do not clash with other more senior royals before attending any family gathering or private function.
Our source said: “Meghan’s every move is now dictated, and she has even been told to stop wearing her beloved trouser suits as the Queen dislikes them on women.
“These are exactly the kinds of rules that drove Princess Diana round the bend, so in a way Meghan’s estranged dad is right about her being stifled by the royals.
“Maybe that’s why she’s so angry at her dad – she knows deep down he’s telling the truth about her new life.”
Meghan has spent her life campaigning for women’s rights and declared herself a “feminist” on her official royal biography web page.
But according to the source she now spends her time “biting her tongue” about royal restrictions.
The insider said she is also obeying orders as she is “deeply embarrassed” by her dad’s latest outbursts about her new life.
They added: “Meghan would love to throw a huge strop and try and put her stamp on the royal family, but with her dad constantly embarrassing her, she knows she has no cards to play and has to shut up and take everything that’s thrown at her.
“It's extremely hard for her as she used to be a free spirit who loved yoga and her independence when she was an actress.”
Royal aides are now planning to reach out to former Hollywood lighting director Thomas to ask him to stop giving interviews about his daughter – and Meghan is said to be considering cutting him out of her life forever.
The source said that on top of the pressures caused by her dad, she still has to maintain an “icy exterior of calm” and politely negotiate “mind-numbingly boring details” such as negotiating up to four different daily outfit changes with other members of the royal family, as they often change between meals.
Meghan has already been taught techniques about how to get out of cars and how to sit at public engagements so she does not reveal too much of her legs.
Navigating bewildering royal protocol was a major hurdle for Princess Diana when she married Charles.
She told her biographer Andrew Morton that after her engagement to the Prince of Wales: “I cried like a baby to the four walls. I just couldn’t cope with it.”
And when Diana’s personal protection officer told her the night before the engagement was announced that it would be the last evening of freedom she would ever have, Diana said it was “like a sword went in my heart”.
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