Shakedowns of Shakespeare scramble the settings. Here’s Romeo and Juliet as cokehead Californians, King Lear as a cattle baron, and Titus Andronicus as an ombudsman. But the text remains sacrosanct – Emma Rice’s nibbling at the pentameters of A Midsummer Night’s Dream irking Globe purists as recently as 2016.

So I was surprised when, at the end of March, the director Wils Wilson invited me, a stand-up comedian, to collaborate with Shakespeare himself, who needed some jokes beefed up in Macbeth, her debut for the Royal Shakespeare Company.

Wilson wanted to retool the comic turn, the gatekeeper called a Porter. “The jokes are pretty unintelligible now,” she said. “English tailors and French hose? Executed Jesuit priests? I want them to be understandable, satirical and funny, but in that sinister, dark way they are in the original. The Porter is the gatekeeper of Hell after all.” I canvassed opinion.

My son, earbud-deep in Macbeth GCSE, said: “That makes sense. Obviously Shakespeare’s clowns were different in every production, and fitted in what was then in the news.” So I accepted Wilson’s offer. And unlike the anonymous acts who write the panel show shtick and stadium spiel of popular comedians, the RSC was to credit me, though not exactly as I asked, “Macbeth – by William Shakespeare, with additional funny material by Stewart Lee” proving too much of a reach.

Wilson’s offer reawakened my adolescent entanglements with Shakespeare. In 1980 my mum, sensing I had ambitions beyond my station, took me to see my first ever Shakespeare in Stratford. Donald Sinden blacked up as Othello, the last white actor to do so at the RSC. A 12-year-old Specials fan, I had an inkling that things were changing. Some aspects of Shakespearean practice could benefit from updating. But our next RSC trip fried my teenage mind.

Howard Davies’ Macbeth had everything the teenage post-punk could want: a chrome scaffolding set; guys in polo necks playing LinnDrums like Tubeway Army; and Josette Simon, who all adolescent boys fancied in the ropey BBC sci-fi Blake’s 7, as a witch in a leotard.

Unsurprisingly, I now spent my Saturdays on the X50 bus, snagging £5 standing tickets to the mid-eighties RSC oeuvre. Ralph Steadman’s visceral Macbeth poster still graces my home 40 years later. Though I’d never given it any thought, it depicts the Porter himself, drunkenly jangling keys, giving me permission.

As did Wilson. “The scene is a complete one-off – unlike anything else in Shakespeare. Some say it’s the invention of stand-up, though I am sure that’s not true,” she offered. “The material is dark, satirical, current, political, risky, dealing with hypocrisy, lies, morality, sex, drunkenness – all the good stuff. And the Porter breaks the fourth wall and speaks directly to the audience. No one else does that in the play except Macbeth. And it is – apparently – when the knock, knock joke was invented.”

Wilson had already cast the fearless Scottish actor Alison Peebles as her Porter, which helped. I remembered comedic avatars of judgment, similar to the Porter, that I had seen over the years. Jerry Sadowitz, attacking the values of every section of his hell-bound crowd; and the feisty female Scottish comedians who impressed me as a younger man – Lynn Ferguson spitting fire as resident compere at the Red Rose in Finsbury Park 30 years ago, the velvet gloved fist of Janey Godley, the gatling gun offence of the much-missed Jane Mackay, destroying drunken audiences after midnight at The Stand in Edinburgh in the 90s. In homage to these voices, I swapped out the corrupt tailors and judiciaries of the original for the damned-to-hell celebrities, politicians and grifters of today. And I got in two covert lines of Lenny Bruce’s, a private joke for myself.

The second section of the scene, when the Porter engages in a torturous riff on impotence with Lennox and Macduff, is like a music hall “front curtain” act, performed while the scene behind resets. Are we waiting for Macbeth to wash off Duncan’s blood?

In 1979, the year before I saw my first Shakespeare, I saw my last childhood pantomime – Les Dawson and the variety survivor stooge Eli Woods in Babes in the Wood at the Birmingham Hippodrome. Three years later I saw the Comic Strip’s Peter Richardson opening there for Dexy’s Midnight Runners, by which time the cocksure alternative comedians had dated Dawson’s gently Rabelaisian routines. Wading curiously through old clips years later I saw a gangling Woods, a sparkling Roy Castle, and a curmudgeonly Jimmy James doing Jimmy Jewel’s definitive “giraffe in a box” bit on a 1970s Parkinson. It seemed oddly familiar.

Was it possible Woods and Dawson had hand-cranked the routine into their panto? Inspired, I approached the Porter’s interaction with Lennox and MacDuff as music hall cross-talk, taking care to keep the non-mechanicals banter in iambic pentameter.

On Friday, I’ll have my first privileged look at whatever Wilson and Peebles are doing with my now orphaned text. But replaying the Porter scene not as a stifled Shakespearean set piece, but as actual live comedy, means it will only exhale when it meets an audience. And then, in the days before press night, it will require the same rapid reassembly actual comedians routinely apply.

It’s an incredible experience for me, being asked to contribute to Macbeth. I wish my mum could have seen it. The lock of her Austin Maxi froze, I remember, in the snow of the frozen pre-climate-change, post-Macbeth RSC riverside carpark, and she told me to piss on it to free it up. She would have been proud of how that theatre trip paid off. I emailed my old English tutor, in contrast, the day after Wilson’s offer, to tell her the news. It was 1 April. She assumed, all too perfectly, that it was an April Fool. Remember the Porter.