The ‘special relationship’ between the UK and the US has weathered many global crises and personality clashes over the decades, but it arguably reached its zenith in the 1980s, when Thatcher and Reagan forged a unique friendship that grounded their political strategising in mutual respect.

Thatcher biographer Charles Moore, who was The Telegraph’s political correspondent throughout the era, traces their relationship through a turbulent decade of global political upheaval reshaped by UK and US efforts to thaw East/West relations and ultimately work towards tearing down the Iron Curtain.

But don’t expect a personal polemic. The doc, which airs on BBC2 this spring, is a pacy retelling of the era that extracts humour from its interviewees and humanises its subjects. Filmmaker Chris Durlacher, behind Emmy-winning George Orwell – A Life In Pictures, is attached as series producer and director.

“It’s a very warm, personable piece and Charles secures great access to, and emotion from, their politicians and their close aides,” says Magnify Media head of sales and co-productions Anthony Appell. “I like the fact it’s not his views, but the words of those who knew them best.”

Thatcher was and remains a divisive figure, but Appell believes this doc can be filed alongside her portrayals by both Meryl Streep in the film Thatcher and Gillian Anderson in The Crown as a three-dimensional portrait of a resilient leader.

“She cuts an aggressive, pushy figure who wasn’t to be bullied by any leader,” Appell adds. “But the interviews she gave to camera offer a warmer look at her. She’s quite vulnerable at times when she’s in conflict with Reagan and doesn’t have her allies around her. I find it endearing and personable – I learned a lot from it.”

Reagan, meanwhile, comes across as “a very big, easy-going, tolerant guy”, who knew how to handle Thatcher, and vice-versa. His words were always “just let her be”. “He thought of her as the perfect English lady - even though he couldn’t get a word in edgeways,” says Appell.

The doc’s global appeal is evident, and the shorter international cut (2 x 50 minutes, minus some archive) has already been subject to a bidding war in Australia – won by public broadcaster SBS – and the US, where it has an as-yet unnamed, VoD home.

Plimsoll is known globally for its blue-chip natural history (such as Netflix’s Night On Earth and ITV’s A Year On Planet Earth) and this doc signals a new direction under head of documentaries Richard Klein – exec producer on the series – and potentially a returning format.

“Richard’s a genius and I hope this will be the first of many from him in this sphere,” says Appell. “There is talk of other relationships we might be able to work up if this is successful.”