Orthodox son-in-law acts as peacemaker

Kushner has now become an essential cog in the highly unorthodox Trump political machine, as the candidate himself has publicly acknowledged in the manner only he can.

Kushner's work is driven by family, not ideology

"Jared is a very successful real estate person," he declared while conducting his victory lap on the night he sealed the Republican nomination last month, "but I actually think he likes politics more than he likes real estate. He's very good at politics."

In private, Trump is not always so fulsome. When a planned visit to Israel last December went awry after Benjamin Netanyahu publicly attacked Trump's plan to ban Muslims entering the US, the candidate laid into Kushner, saying: "This was all your idea."

Kushner is Trump's designated peacemaker. He is widely credited with having helped craft the speech which helped to soothe the rattled nerves of Aipac when Trump addressed its annual convention in March.

Earlier this month, Kushner played a part in writing what were described in the US media as the "unusually polished" remarks - like those at Aipac, delivered with the aid of a Teleprompter - which Trump made on the night of the California primary as he tried calm the outcry in the Republican party over his attacks on the "Mexican" judge presiding over the Trump University case.

Kushner has also helped to rebuild the bridges Trump has gleefully set alight throughout the primary season. He accompanied the candidate when he met Republican congressional leaders, including House Speaker Paul Ryan.

Kushner is said to have wooed other members of the Republican establishment, such as Henry Kissinger, whom Trump has roundly abused, and attempted to repair the damage done to relations with Rupert Murdoch by his father-in-law's attacks on the media mogul's Fox News network.

Reports suggest that Kushner is helping vet the candidates Trump is considering as his running mate and has been charged with putting together the transition team which will be assembled if Hillary Clinton is defeated.

But Kushner's work for Trump appears to be driven by familial ties, not ideological affinity. Like his father - from whom, like Trump, he inherited his real estate empire - Kushner has long been a supporter of the Democratic party.

In a 2004 profile, Kushner spoke of his admiration for John F Kennedy, a picture of whom hung in his office.

Two years ago, he gave $10,000 to both the New York and New Jersey state parties as well as donating to the campaigns of a senator and a Congress candidate. Kushner and his wife were also supporters of the pro-gay marriage Freedom to Marry campaign.

In many ways, Kushner is, as Vanity Fair put it, "the anti-Trump Trump". Thrust into running the family firm at the age of 23, when his father was jailed for tax evasion and witness intimidation, Kushner displayed Trump's business acumen and media-savvy.

In his mid-20s, he bought the then-money-losing New York Observer, recognising the kudos attached to newspaper proprietorship. Shortly after he paid $1.8bn (GPB1.2bn) for a Fifth Avenue office tower, then the highest price for a single building in New York, but was careful to put little of his own money into the deal. But, in most respects, Kushner bears few resemblances to his father-in-law. He shuns media interviews - he's said little about Trump's candidacy other than that he thinks he'd be "great" - and is said to be faultlessly polite and never lose his temper.

As one business partner said: "A lot of times, when I'm with Jared, I take cues from his behaviour just to learn how to act... just to act a little bit better myself."

So far, Donald Trump doesn't appear to be doing likewise.