A plate featuring a sketch of Dorothy the Dinosaur hangs above Diethnes' stairwell. It's dated 2006 and signed by the Blue Wiggle, Anthony Field, who "enjoyed a meal here" once, a plaque informs diners.

The same year Wiggle Bleu was drawing on dinner plates, another fan of Pitt Street's oldest Greek restaurant, Roger Rogerson, was released from prison, the crooked cop having served 12 months for giving false evidence to the Police Integrity Commission.

Rogerson was reportedly a Diethnes regular because its stucco-walled basement location made it difficult for a surveillance unit to eavesdrop, but easy for a bloke with enemies to monitor the entrance.

I'd wager the Blue Wiggle was just keen on moussaka.

Diethnes opened in 1952 on the wave of Greek immigration. It was one of the first Hellenic eateries in Sydney that wasn't a milk bar, along with the Athenian on Castlereagh Street and New Hellas on the corner of Liverpool and Elizabeth, where authors and Bulletin journalists would meet daily to swap stories and cigarettes.

Greek cuisine was painted in broad strokes during the Menzies era and Hellenic restaurants often listed wiener schnitzel and spag bol next to spanakopita. Diethnes still offers veal scallopini ($28.90) if you're keen but, for the most part, the menu is chock-full of comforting Greek classics as Hestia intended.

The Ventouris family is at the heart of Diethnes. Phillip Ventouris, originally the restaurant's dishwasher, bought the business in 1960. John Ventouris (son of Phillip) took charge of the business in 2000 with his wife, Hellan​, and has kept the capsicums stuffed ever since.

Diethnes moved to its current bunker location from a site across the road in 1977 and little has changed about the interiors in that time. Corinthian columns and amphora vases decorate a long, wide room blessed with louvred fake windows and an Aegean Sea mural. There are vines on the ceiling and statues from the late copper art period of Greek design. I love it.

The floor is managed by a team of wildly varying ages and everyone is committed to guests leaving happy and full, but not too full. I'm told by one of the senior waiters that extra lamb's fry is a bad idea. "You order too much already!" Indeed. It's also worth remembering that ekmek kataifi ($9.90) is a filling dessert of syrupy, spindly kataifi pastry supporting custard and pistachios, and you must absolutely add it to the bill – perhaps with a Metaxa brandy, served warm, to cut through the cream.

Traditional moussaka ($22.90) is a straight-up delicious slab of properly seasoned beef mince and potatoes topped with a tomato-based sauce, sliced eggplant and bechamel – the best parts of lasagne and shepherd's pie combined. With a Greek salad ($14.10) on the side, it would be a banging lunch for one, but Diethnes is not a place for dining solo. It's for family dinners, long lunches, end-of-financial-year steam-blowers and ordering enough dips to feed a Trojan army.

A mixed mezze plate for two ($24.90) is enough for four, and includes soft triangles of pita destined for swiping through garlic-heavy tzatziki and a salmon-pink taramasalata sharpened with lemon juice. The platter also heaves with meatballs, zucchini fritters and fried haloumi because why shouldn't it? The warm embrace of too much haloumi is why you come to a Greek restaurant in the first place.

You also come for the lamb. Specifically, at Diethnes, pan-fried lamb's brains and chips ($22.90), lamb casserole ($27.90), lamb souvlaki ($29.50) and – best of the lot – slow-roasted lamb shoulder ($31.50) brushed with olive oil and oregano and served with baked potatoes you could slice with a spoon. It's the kind of rustic cooking found in Cyclades tavernas accessible only by donkey.

Diethnes survives because the Ventouris family knows Greek food should not to be trifled with. These are domestic recipes spanning generations, without the need for emulsions and garnishes of no relevance (I'm talking about you, red veined sorrel).

The only thing Greek food ever needs is a warm environment where you can enjoy it with people you care about – whether that's family, band mates or fellow detectives on the take. Kali orexi, Diethnes. Thank you for the memories and the moussaka.

Est. 1952.

Signature dishes: spanakopita ($11); lamb souvlaki ($29.50); lamb shoulder ($31.50); moussaka ($22.90); mixed mezze plate for two ($24.90); ekmek kataifi ($9.90);

Famous diners: John Ibrahim, Anthony Field, Murray Cook, Mary Coustas, Roger Rogerson, John Howard.