While constant rebirth is key to the success of a fashion house, heritage plays a huge part in keeping the prestige alive. What would Louis Vuitton be without those trunks, Yves Saint Laurent without Le Smoking, or Chanel without its legendary founder?

This morning in Milan at the Triennale Design Gallery, Ermenegildo Zegna held a special showing of its eponymous and Z Zegna labels, celebrating 100 years in the business.

It was a momentous occasion, the first time the two labels had been shown together in the family's hometown, and the first time they'd shifted location away from the company offices (apparently the Zegna family and friends plus all the usual suspects wouldn't have fit).

I was seated alongside an elegant older lady who informed me with a smile that she was "Part of the family." French film star Jean Reno sat nearby, he was a friend.

The show began with Ermenegildo Zegna, the more deluxe of the two labels.

This was a wardrobe to outfit a whole raft of archetypal heroic male characters. For the intrepid explorer, linen shirts and pants in earthy tones of rust and ochre. For the playboy billionaire, precision cut navy double breasted blazers and white trousers. For the travelling man, nylon pants with drawstring waists, chunky cotton sweaters and leather sandals.

A full range of suiting was presented from seersucker to brilliant blue, white linen and burnt orange cotton, the best of which had shrunken jackets and fuller trousers.

Luxury was served up in the form of buttery tan leather coats paired with white cotton trousers, hemmed above the ankle; and the finest gauge cashmere, so light, it was virtually transparent.

It was a bold collection filled with vibrant colours and masculine garments - this was a full wardrobe for a real man. A real man with means (luxury like this don't come cheap).

The younger Z Zegna collection came next. True to form, it was the cheeky little brother to Ermenegildo's relaxed leading man.

Got your suit dirty? No problem, just stuff it in the washing machine. Don't own an iron? Never fear, just wear it as is. Crushed cotton and linen blazers were de rigeur, with rolled pants, short shorts or cuffed jeans.

Exposed tailoring details is a Z Zegna signature and their were plenty of them, from outer darts on suits to an inside-out peacoat.

My favourite pieces were the cotton double breasted blazers - not an easy garment to pull off, but the perfect summer blend of casual sophistication. They appeared in brick red, charcoal, and grey with contrasting cream sleeves.

The entire family took to the catwalk after the finale, enjoying the well-earned applause that comes with 100 years of success.

If they can keep producing collections like these, 100 more wouldn't be out of the question.

*****

There's always a bit of a wait outside Gucci, one of the hottest tickets of the week. Held at midday in a hotel on the corner of a particularly busy intersection (trams, trains and taxis form a pedestrian's hazard), the scene outside is always well worth a watch.

Italian catwalk photographers sit on their giant camera cases grumbling obscenities at the black-suited security men; hordes of street-style bloggers descend upon the better-dressed masses, then collectively sprint as they spot that girl in the latest McQueen dress; American editors stand around shooting the breeze, their khaki pants expertly rolled above desert boots (worn sockless). Then the call comes, 'Doors are open!' and the pack heads inside, past the foyer where champagne is served, and into the show room to search for their seats.

Gucci's mood for spring was casual luxury - kick around clothes for the young monied - henley tees under suits, nothing under leather jackets and safari shirts worn open at the neck. Brand staples like chunky knit cardigans and sweaters were present, with pulls hanging off the backs as if the night before had ended a little too well.

Sure, there were the more lavish pieces, like a deluxe sweater in suede or a brown snakeskin button up, but even they were paired with jeans. Yes, jeans. Blue jeans and cream drill jeans, not dissimilar from the types worn by Marlboro men on 1970s billboards.

The 1970s metaphor extended to a couple of shirts and a blazer, all emblazoned with the kitschy-cool Gucci scarf prints you can still find in off the beaten track op shops.

It was a quieter collection than the overt luxury of fall, but decidedly more wearable than a leopard print blazer. Only one question remains: who will don the jeans first? My money's on Kanye.

There's no better end to a day in Milan than an Etro show. First up, they feed and water you (sandwiches, fruit salads in tiny jars and grapefruit juice).

Next, they do something fun with the catwalk - last time it was sand, this time grass.

The great thing about Etro is they don't take themselves too seriously. They have fun with their shows. Quelle horreur; the models even smile!

The collections are all about hunky men not shying away from their hunky-ness. That means: paisley printed shirts in the sheerest silks (worn open to the waist), short shorts, wind-swept hair and vibrant colours. You can't spell resort without Etro.

The most interesting piece of the lot was a new take on formal wear - a tuxedo onesy a la Max from Where The Wild Things Are. Just don't drink too much in it, those things are a nightmare to get in and out of.

You can tell the models love doing these shows because they happily dance the length of the catwalk with the designers during the finale.

And while the crowd claps, it's nothing like the cheers that are heard backstage after the show. It's what summer's all about - celebration.

I think it's time I went out and did some of that myself.