Twenty-five years. A life sentence. A man freed after 25 years in jail would see the world through quite flabbergasted eyes. What would he make of, say, contactless bank cards or Tinder or Paddy McGuinness? Yes, his would be a fascinating perspective (the convict's, not Paddy's).

Since I’ve been asked to fill in on BBC magazine show This Time, 25 years after my last BBC presenting gig, it occurred to me I’ve served my own life sentence. Perhaps not the kind demanded by the family of the man I shot dead on air, but a life sentence nonetheless. And like the newly freed convict I mentioned in paragraph one, my time away leaves me well placed to consider how the world (of TV) has changed and turn it into this thinkpiece for GQ.

In it, I will look at the rise of multichannel, HD technology and diversity – the key drivers of what Alan Shearer calls “the medium’s discernible paradigm shift”. I will touch on the BBC’s funding model, the rise of streaming and the insistence of quirky regional accents for on-screen "talent".

I’ll come to all of these shortly, but first a brief word on refreshments. Because the most obvious difference between then and now is the sandwich selection at lunch!

The BLT comes with bacon so floppy and undercooked the rind is translucent and resembles silicone jelly. It’s, to my eyes, absolutely disgusting.

In the Nineties, we came live from Television Centre in Shepherd’s Bush, but with that building now turned into ace apartments owned by people who don’t live there, the BBC has upped sticks to New Broadcasting House, Central London. Back at TVC, lunch was limited to something-with-chips in the BBC club or a panini from the ground floor cafe. Beyond that, well you were stranded in the no-man’s-land of West London. What could you do? Venture into Shepherd’s Bush, with its chicken shops and outdoor market? Risk a fry-up from a cafe with chairs screwed to the floor?

No. Lunch back then was a miserable affair. Little wonder BBC presenters made do with a liquid diet, rendering them tipsy enough in the afternoons to commit the industrial-scale sexual harassment for which the Corporation is now famous.

Since the Beeb’s relocation, though, we’re bang smack in the heart of London’s lunching district, with a cornucopia of choice for even the most discerning sandwich fancier. Not keen on grabbing a bite in the BBC’s subsidised cafe? Fine. I invite you to walk down Regent’s Street and marvel at the choice of branded sandwich outlets.

Look to your right and you’re greeted straight away by the mustard-yellow sign of an Eat. These guys don’t muck about and it’s little wonder they punctuate the name with a full stop – a reminder, to me at least, (when you’re) full, stop. Now, Eat always sells a good sarnie. The team there opt for a thick-cut granary, a superb all-rounder and the perfect loaf for a really, really satisfying sandwich. If you’ve no meetings that afternoon and aren’t worried about your breath, try the tuna and cucumber, the vinegary flakes of tuna meat set off by chunks of cool, refreshing vegetable. Are its sandwiches perfect? No. The BLT comes with bacon so floppy and undercooked the rind is translucent and resembles silicone jelly. It’s, to my eyes, absolutely disgusting. But that’s a mere blip on an otherwise faultless sarnie setup.

Connoisseurs will quibble at my classifying a burger as a sandwich, I stand by it. It’s meat wedged between bread; and, I’m sorry, that is a sandwich.

Don’t fancy Eat? No problem! Cross the road and you’re welcomed by the sight of a Pret A Manger ("Ready To Munch"). When it comes to butties, Pret and Eat are two peas from the same pod – a notch up price-wise from your budget offerings – and hard to separate. Perhaps Pret is a smidge more generous with the mayo spoon, perhaps its bacon is given a touch longer in the pan, leaving it less flaccid and see-through than that of its near neighbour. But Pret and Eat are great options and I have no hesitation in recommending them.

Want more? You got it. A few yards south, you’ll find Starbucks, the tax-canny US coffee chain whose sandwich range, while limited, is well worth checking out if Eat or Pret ain't yo thang.

Those who like their sandwiches hot and round might like to try a "burger" from quick-food giants McDonald's – and while connoisseurs will quibble at my classifying a burger as a sandwich, I stand by it. It’s meat wedged between bread; and, I’m sorry, that is a sandwich. Try the chicken sandwich (I shan’t add the Mc) for creamy white, piping hot breast meat in a zingy, flour-based coating. Finger lickin’ good.

Back across the road, for those with more money than sense, you can pick up a sandwich from an array of shops that together sound like the members of a bad boyband: Leon, Paul, Joe (& The Juice). The latter in particular isn’t my bag. Staffed by preening take-your-timers, it’s a coffee and smoothie shop for those whose answer to the question “When would you like your drink?” is “In about ten minutes.” But if pushed, you can buy sandwiches from any of them and that’s something to be celebrated.

You can pick up a sandwich from an array of shops that together sound like the members of a bad boyband: Leon, Paul, Joe (& The Juice)

Think the list ends there? Think again. Toddle into Topshop, take the escalator down past the bras and sandals and what’s this? Another Eat, less than 300 yards from the last one, a quirk of branch strategy for which someone at head office must have been torn a new one. It’s not quite as roomy as the flagship restaurant I mentioned earlier and, being an in-store concession, your sandwich is going to be accompanied by the taste of perfume, but it’s a great option for those in a rush who have ducked into Topshop to use the toilet or hide from an associate.

So that’s sandwiches dealt with. But what of the myriad other changes in the world of television?

Oh, and there’s Boots as well. Lots of people overlook Boots when it comes to sandwiches, but don’t overlook Boots. Although pre-packed on a worryingly vague earlier date, these tasty, well made bread snacks are lightyears better than they were in the past, when their sandwich offering was blighted by a practice known as "central packing| - an all-too-common ruse that sees the filling bunched into the centre of the sandwich. When sliced through the middle and presented in cross-section, it gave the illusion of a plump, generously filled sandwich. It’s only after buying one that you find the filling tapers at the edges down to a barren tundra of unoccupied bread. Whether it was due to my letters or some other reason, Boots are no longer guilty of this and are now a byword for quite excellent pre-packed sandwiches.

So you see, today’s BBC telly makers enjoy a breadth of sandwich choice that their Nineties counterparts could only have dreamt of.

I had hoped to discuss other changes in television but I’ve hit my word count now. Thank you.

This Time With Alan Partridge starts on BBC One tonight, Monday 25 February, at 9:30pm.

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