Forget "It" bags, WAG bags, eco bags, bags for life and "I'm not a plastic bag" bags. There is only one bag that matters right now. It is a bag emblematic of a world in upheaval and of a rapidly changing Britain.

You may own one yourself for use as a laundry bag, to store bedding or for holiday packing overspill. But even if you don't, its ubiquity will make it instantly recognisable; a zip-up square of woven plastic in a variety of coloured plaids and stripes, negligible in weight and easily folded away, but capable of enormous volume, available from Pound Shops, hardware stores and the like.

Its manufacturer (Zhejiang Daxin Industry Co. Ltd, China; minimum order: 10,000 units) describes it simply as a tote bag, but it has a multitude of names depending on geography.

In Ghana, it is known as the "Ghana must go" bag; in Germany it is "Tuekenkoffer" or the Turkish suitcase; in America, the "Chinatown tote"; in Guyana as "Guyanese Samsonite" and elsewhere as the "Bangladeshi Bag" or the "Refugee Bag".

The sobriquets are telling. It is the bag of the uprooted, willingly or otherwise, of those in search of a better life who are ready to work for it, or of an easier life courtesy of others. Right now, you can see these bags piled up in airport arrival halls around Britain, or stacked on luggage trolleys at train stations. London's streets, and those of other cities, are full of people weighed down by them.

At 9am yesterday at Victoria's "Hell Corner" - where the cross-currents of commuters, tourists, travellers and newly arrived migrants clash as they fight their way between trains, Tubes, buses and the coach station - two scruffy little boys stood dwarfed by three of the bags.

Mesmerised by the bendy buses, one wandered towards the road, only to be shouted back by his older sister, who was carrying another of the bulging bags. Her mother was somehow managing three. Behind her was the grandmother, stooped and wrinkled beyond belief, but managing her own plaid tote. Eastern European, certainly, and undoubtedly poor.

My first thought was: "They're here to stay." And the second: "They're doing exactly what I'd do if I'd grown up in some poverty-stricken hell hole and there was a way out."

As my colleague Jeff Randall argued yesterday, unrestricted immigration has worrying implications for housing, healthcare and education and essential services. There are mutterings of an amnesty for illegal immigrants and that is, surely, the only practical way forward while also securing Britain's borders.

But for those already here - well, the majority didn't make the journey so they could stay at the bottom of British society. The cheap, plastic bags they haul after them, overflowing with their belongings, are the modern equivalent of the battered leather suitcases piled high at the Ellis Island museum, a symbol of the self-interested determination of the immigrants who built America.

Anyone who has the ambition and aspiration to come here will not be satisfied with a tote bag for long. They'll be moving on up - to fake Louis Vuitton and then, one day, maybe Louis Vuitton itself. And yes, there is an LV version of the "Ghana must go" bag. Known as the Street GM, it costs £1,400.

Kate's close escape

Was there ever a girl who delighted more in her freedom than Kate Middleton? In the immediate aftermath of her break-up with Prince William, her appearances at various Chelsea nightclubs seemed a touch contrived.

There was no attempt to avoid the paparazzi, she forced a smile and the message was "I am having a good time. I am, I am. Honest. Not missing him a bit." Her demeanour on a visit to the Badminton Horse Trials last month, carefully timed to avoid William, who came the day after, was a touch forlorn: "I should really be here with him."

Not any more. Suddenly, the realisation of what she has escaped - marriage into one of the world's most dysfunctional families, to a man who runs a high risk of turning into his father despite the best efforts of his mother, and a life of endless scrutiny - has dawned on her.

No more tweedy suits or demure dresses - this week she was out in the skinniest of white jeans, beaming at the cameras and indulging in the most potent cocktails.

In one sense, though, she hasn't moved on. Her companion in the taxi home looked awfully like the Prince. You're not quite there, Kate - but stick with it, and soon you'll have kicked the Windsor habit entirely.

A world of delusion

'I would never regret it. How could I? We were all hurt by it, but I had the courage to follow my heart and soul and I can look back now and know I've done the right thing. There's a very strong bond between us."

Oh, I can hardly wait. Alastair Campbell's expletive-free diaries promise to be the highlight of the summer, the truth at last about him and Tony. Be sure not to miss the extracts he'll be reading on BBC2 in July (I thought he hated the BBC?), and expect much more along the lines of "He's always there for me. He's someone I can trust and rely on completely."

Oops, sorry, no! Some mix-up here. That was Nancy Dell'Olio talking about Sven in her newly published memoirs (and I guess he was always there for her, except when he was with Ulrika. Or Faria). But it was an easy mistake to make. Both Nancy and Ali operate in a world of delusion. She is the victim of hers. Others were the victims of his.

Aren't Catholics tolerable?

During the longest and most desperate of months, Kate and Gerry McCann have clung to the faith that sustains them and fosters their hope of finding Madeleine. This week, in the eyes of some, they went too far, and a very public display of their religious affiliation - an audience with Pope Benedict XVI in Rome - seems to have unleashed a backlash.

Suddenly, the cordon of respect and sympathy that has safeguarded them from criticism thus far was broken. It wasn't quite open season on the McCanns, but it felt like it.

"How different things would be if they were an inarticulate pair of chavs"; "They are bad parents who left their children alone at night"; "They've become celebrity junkies"; "How did Kate find time to have her highlights done?"; "Aren't they both a little too composed" etc.

"It's all got a little weird, now," was one of the milder comments I heard while watching the Pope bless a picture of their daughter.

I may be a paranoid papist, but there is a whiff of something rather unpleasant about this. I understand how the "bells and smells" accessorising of Roman Catholicism is alien - even distasteful - to many, but when not a day passes without some public figure making a plea for tolerance and understanding of other faiths and cultures, there is scant evidence of its application to a homegrown variety.

Whatever you do, don't mention the war

All hail, Tony Blair, the Paramount Chief of Peace of Sierra Leone. I wonder how the parents and fiancée of Cpl Darren Bonner (far left) felt when they saw the PM's grinning visage atop his flowing robes. Cpl Bonner acquired a new title, too, this week: the 50th Briton to die in Afghanistan in a year. The men serving alongside him say they are fighting a war that no one in Britain wants to know about.

Well, if you're a newly crowned Chief of Peace, you wouldn't want to remind anyone of that little conflict, would you? And certainly not while your erstwhile loyal government and Commons colleagues (Blears, Hain, Harman, Benn, Johnson and Cruddas), in their desperation to be deputy leader of the Labour Party, are doing their very best to leave you carrying the can for the far bigger one still haunting you.