During their joint press conference on Monday, the Irish prime minister, Leo Varadkar, appeared to gently tease his British counterpart, Boris Johnson, with a passing classical reference that caught the ear of some commentators.

Varadkar told Johnson: “Negotiating FTAs [free trade agreements] with the EU and US and securing their ratification in less than three years is going to be a herculean task for you. We want to be your friend and ally, your Athena, in doing so.”

Johnson smiled as Varadkar made the comment, although it is unclear whether it was because the British prime minister was pleased to see Varadkar aping the Johnson style of frequently quoting the classics, or whether he had really taken in the implications of what the Irish prime minister had just said.

In Greek mythology, the goddess Athena did assist Hercules as an ally during the performance of his 12 labours. She provided, for example, bronze krotala – noise-makers similar to castanets – to help him scare off the flock of Stymphalian birds. And in some versions of the tale she was also of service to him by returning to their rightful place the golden apples of the gods that Hercules had been asked to obtain.

But it is perhaps her most dramatic intervention in the life of Hercules that Varadkar was obliquely referring to.

Hercules was obliged to perform the 12 labours as an act of penitence after he had descended into madness and murdered his wife, Megara, and his children. At the moment he was about to go on and kill the man who had fostered him, Amphitryon, Athena intervened. Seeing that he had gone mad, she struck Hercules down and knocked him out to prevent him causing more bloodshed and doing more damage than he had already done.

Very much what you would hope for from a friend and ally, but maybe not what you would want to hear on the international stage at a moment of tense diplomacy.

Facebook Twitter Pinterest Boris Johnson reacts during the joint press conference. Photograph: Charles McQuillan/Getty Images

Varadkar’s deployment of Greek mythology is open to interpretation. However, his other words in the press conference were very clear indeed: “The story of Brexit will not end if the United Kingdom leaves on 31 October or even 31 January – there is no such thing as a clean break. No such thing as just getting it done.”