It would be humble of me to say that I am still learning my craft. It would be humble – but untrue. Because I think I know quite a lot about my craft: the craft of acting. Benedict Cumberbatch said to me recently, “I don’t know how the fuck you do it.” It got me to thinking, “How the fuck do I do it?” I duly analysed my secrets of successful thespianship and present them to you here.

Be good at acting

Although largely forgotten now, the Jamaican actor Bennet Carnival was probably the finest Othello I’ve ever seen (excluding Lenny Henry). One of the original Windrush immigrants, Bennet had it tough when he first came to London at the age of 65. No sooner had he composed a jolly calypso tune onboard the ship, enthusiastically celebrating the joys of the capital, he found himself the victim of shocking racism. On searching for a bedsit in Notting Hill, he was greeted with signs on doors exclaiming: No Dogs. No Irish. No Bennet Carnival. This gentle man from a remote village, where even a simple amenity like running water was unknown (apart from rivers), was possibly the finest and most instinctive actor I have ever known. Paul Scofield, on seeing him in an early production of Lionel Bart’s Oliver! (in which Bennet was badly miscast in the title role) was moved to remark, “He’s really good at acting!” It was a lesson which I’ve always passed on to younger actors: be good at acting.

Don’t open that fourth bottle of wine

Every actor worth his salt goes onstage drunk at least once in his career. Presuming that you intend to tackle your role while inebriated for whatever reason – a grudge against the director, a bad review or contempt for the audience all count – I would regard 10 pints of beer as the absolute limit. Vodka I would restrict to a litre, and wine to three bottles max. Before teetering on, make sure you know where the audience are; to your right or to the left. Don’t be tempted to say hello to them. I did this once during a production of Uncle Vanya and found it impossible to get back into character afterwards. Also, make sure you’ve remembered which play you’re in. Early in his career, Richard Burton famously played the part of Abraham Slender, the foolish suitor to Anne in Shakespeare’s The Merry Wives Of Windsor during a production of Look Back In Anger. He was so pissed he actually thought he’d got away with it, but even an audience with a below average appreciation of the theatre would know there was something up when they see a Shakespearean character in full costume crowbarred into a 1950s kitchen sink drama.

Sex scenes: always pack an extra sock

I have never turned down a role because it required me to portray (or, in one case, to actually perform) a sexual act. Among the people I have portrayed “sex” with are Diana Quick, Amanda Donohoe, Hattie Jacques and Simon Callow (for a Comic Relief “skit”). People are usually pretty jealous when they hear that I’m about to take on a job which requires me to make passionate love to Diana Quick (in that particular case, an episode of Minder where I played the pompous brother of the posh bird to whom Terry took a liking), but I can tell you, it’s bloody hard work and usually not “sexy” at all. Every male actor knows that when he is contracted to perform a sex scene for a television programme due to be screened before the watershed, he should always take along three socks. One for each foot and one to cover the area which could cause offence if left unmasked. Some years ago, filming for Howards’ Way, I forgot the extra sock and was firmly told by both the director and my co-star to remove one from my foot and place it over my sex part. I protested that this would look ridiculous, but reluctantly complied. As a result of this hamfisted piece of direction and diva-like behaviour from my co-star, the series was not critically well received. A contemporary of mine at Rada, Ray Purchase, a notoriously homophobic actor who has gone on anti-gay marriage protest marches, has a unique approach to work where he is required to portray same-sex love scenes. Before playing the scene, he receives injections into his lips, face and, if his sexual organs are required to be on display, into his groin. These numb the targeted areas and make them unresponsive to touching by other men. I find this approach far too over the top.

Be careful what you endorse

You probably don’t remember Derek Sibling, but he was one of the best actors I have ever encountered. The brightest in his year at Rada, he trod out one of the best Henry Vs I’ve ever seen. All seemed to be going well for him, then, one night during an ad break, as I was watching the results of the 1983 general election, I saw a man bursting forth from my television holding his guts and promoting the benefits of a laxative. The man was Derek Sibling. From that moment on, Sibling was forever linked with the distinctly unglamorous process of evacuating the colon. His dreams of playing Hamlet, of being the next James Bond, of starring in his own family-based BBC1 sitcom, lay in tatters. Nobody is quite sure where Sibling is now, but he’s probably dead. Although I have advertised other products (sponges, honey, agent orange, private prisons, BT shares, poison) no offer (unless it’s a million pounds for a day’s work) can tempt me to promote laxatives.

Steven Toast – ‘Toast of London’ Channel 4