CHRISTOPHER STEVENS reviews last night's TV: Ronnie Kray, Judy Garland and an order the star couldn't refuse 

Secrets Of The Krays

Rating: ****

Kew Gardens: A Year In Bloom

Rating: ***

People say this is the golden age of TV, and they're right. The problem is, it takes a lot of brass to appreciate the gold.

Look at BritBox, a repeats-on-demand service that has branched in to commissioning its own original shows — with an excellent three-part series on the rise and fall of 1960s gangsters the Kray twins debuting yesterday.

BritBox is doing what Netflix set out to do eight or nine years ago, but with a British back catalogue. It offers subscribers access to thousands of dramas, comedies and documentaries from the vaults. If you're an avid TV watcher (why else would you even be thinking about spending your money on BritBox?), you've seen most of this fare before.

Some of it, such as Poirot, Vera, Death In Paradise and a hundred more like them, are regularly shown for free on channels such as ITV3.

Others, from period favourites such as Downton, to marvels like Attenborough's wildlife spectaculars, you might have on DVD.

But BritBox offers just about every boxset your greedy little paws have ever itched to hold. Want to indulge in all the episodes of Doctor Who, going back 60 years? Have a yearning to revisit Tucker and his pals in Grange Hill, or rediscover why Brideshead Revisited and Boys From The Blackstuff were hailed as critical sensations? It's all there.

There's a price to pay. It's £59.99 a year, or £5.99 a month. And like Netflix, Amazon Prime or Apple TV — which have their own – you'll probably have to watch on a computer or a tablet, unless you've got a modern Smart TV.

But if you watch television strictly for the dramas and sitcoms, rather than to keep up with the soaps or the news, the fee is less than half the price of a TV licence.

Secrets Of The Krays (BritBox) is the first of their SVOD (that's streaming video on demand) documentaries. There's nothing extraordinary, but the three 50-minute episodes are packed with information and presented with polish.

It's a smooth, highly professional production, supplying keen psychological portraits from people who knew the London crime brothers, as well as a thorough analysis of how they rose from petty thugs to West End celebrities, with pals in the arts and the Lords.

Society photographer David Bailey and assorted ex-mobsters are among the contributors. 

My favourite was their lawyer, the elegant Nemone Lethbridge — a barrister turned playwright — who recalled her first encounter with them.

In their Italian suits, she said, 'they looked like two owls. They were very solemn and extremely polite'. 

They were also, she added, 'terrific snobs'. The best story came from a cousin. One day, Ronnie Kray — who adored his mum, Violet — brought Judy Garland home. 

'Your song, it's my muvver's favourite,' he said.

This wasn't a compliment. It was an order. In Mrs Kray's front room, Judy performed Over The Rainbow. 

These days, if you want to go over the rainbow, you use a Niftylift — a hydraulic platform, like the one used at Kew for trimming the banana plants.

The gardeners were working in the rooftops of the grand Victorian glass houses, on Kew Gardens: A Year In Bloom (C5). This series uses the techniques familiar from shows such as Secret Life Of The Zoo to tell the stories of staff and exhibits — with orchids instead of elephants.

Naturally, there are statistics by the wheelbarrow. But you can ignore those, and simply enjoy the spectacle of the towering pampas grasses getting their annual trim, and the 10,000 plants in the Temperate House being hosed down.

Pinocchios of the night: Plastic conks, or 'wearable air filters', were on display in Dragons' Den (BBC1). We're told these £85 hooter covers will 'redefine the way we approach breathing'. It seems ridiculous . . . but so did the notion of surgical masks for all.