“I’ve not got a clue who she is – but she’s a snob.” This is how Dan Ware, whose St George’s flag-bedecked house in Strood, Kent, was notoriously photographed by Emily Thornberry, described the then shadow attorney general in November 2014.

It’s an assessment of the Labour MP for Islington South – at once vague and damning – that is now as common in Westminster as it was during that fateful winter in Kent.

Thornberry was ejected from Ed Miliband’s shadow cabinet during the Rochester and Strood by-election, which Ukip won, after she was accused of snobbery. She tweeted the picture of Ware’s driveway, complete with white van, and captioned it blankly “Image from #Rochester”, apparently finding Ware’s outward display of patriotism remarkable.

The blunder exposed a long-time problem in Labour: the disconnection between the London left – the so-called metropolitan elite – and its blue-collar core voters elsewhere in the country. Thornberry, who lives in Islington and is married to a high court judge, became the unlucky pin-up for the worst of the excesses of Labour’s champagne socialist set.

Thornberry, now shadow foreign secretary, was publicly ridiculed again last weekend when she failed to name the French foreign minister during a live interview with Sky News’s Dermot Murnaghan. She also did not know that the president of South Korea is a woman. Rather than confess ignorance, or challenge the presenter on his “pub quiz” questioning style, she accused him of sexism.

“I certainly think sometimes when it comes to sexism, some Sky presenters need to look at themselves . . .” she said, “because you do not do it with anybody else and I do think that it’s patronising.”

Unfortunately for Thornberry, the Westminster village consensus was that her claim of sexism was unconvincing, and she ought to know the names of her European counterparts if she aspires to be Britain’s most senior diplomat.

The right-wing press loathes Thornberry. Like Harriet Harman, she is their worst type of woman – the politically correct, pious and posh type. Although she was raised on a council estate in Surrey by a single mother on benefits, and attended a secondary modern school after failing the eleven-plus, her present wealth has rendered her background irrelevant. The Daily Mail calls her “Lady Smug” and “the biggest hypocrite in Britain” – and says her “property empire” is at odds with her socialism.

She does live in a smart Islington townhouse (the Blairs and that veteran of Islington Labour, Margaret Hodge, once lived on the same road, where houses are valued at £3m) and part-owns two other properties in London. Her husband, Sir Christopher Nugee, provides another source of glee. Tory grandee Nicholas Soames likes to point out that she is properly “Lady Nugee”. The couple have three grown-up children.

Yet the “comeback queen”, as the BBC has described her, has had a tougher return to the front bench than most. Thornberry is the most senior shadow cabinet member who is not an overt Corbynite. She has been a constituency neighbour of the Labour leader since she was first elected to parliament in 2005, and nominated him for the leadership in 2015, but voted for Yvette Cooper. After Corbyn won, she responded by saying that “there’s no point sulking”, after which she got stuck in.

A sharp debater in the Commons chamber, she is also loyal. Her support for both Ed Miliband and Corbyn shows a dedication to making opposition work. She was one of Miliband’s inner circle and during the Rochester scandal it was a sign of his panic that he fired such a close ally.

Born in 1960, Thornberry is an experienced lawyer – for twenty years she specialised in human rights law as a barrister at Tooks Chambers, in London, the set led by the lefty QC Michael Mansfield. An obvious choice for shadow justice secretary under Corbyn, she was given the defence brief instead in the January reshuffle. In true Thornberry style, she chirruped to the press that she didn’t “know why Jeremy gave me this job”, to the chagrin of colleagues whose constituents rely on the defence industry.

Her support for unilateral disarmament was opposed by incredulous pro-Trident Labour MPs and union reps, who decried her apparent lack of knowledge. At a meeting of the Parliamentary Labour Party, hecklers drowned her out and colleagues called her “cringe-worthy” and “appalling”.

Though Thornberry is gaffe-prone, her anger at sexism should not be ignored. She is an easy target because of her gender. There is a sense that some (mostly male) politicians and commentators see her as a smug north London liberal mummy type. They hear her smart vowels. They observe her arched eyebrows, her headmistress-like pout of disdain and her tendency to bomb merrily around Islington on a bike. And they decide that what is more likely resilience and defensiveness must be haughty disdain.

Or perhaps, as she lamented in November 2014, it is just a “prejudiced attitude towards Islington”.