Claire Tomalin, who wrote a biography of the novelist, wonders what he would make of the 21st century

My dear Mr Dickens,

Happy 200th birthday! You yourself were not much given to celebrating anniversaries, but you did go to Stratford-upon-Avon in April 1864, with Robert Browning, Wilkie Collins and John Forster, to celebrate Shakespeare's 300th, "in peace and quiet". And on 30 January 1849, you celebrated the bicentenary of the execution of Charles I with your friend Walter Savage Landor. In so doing, you gave a clear message of how greatly you honoured Shakespeare's writing – "was there ever such a fellow!" – and how heartily you disliked bad government.

Just now, we are all reading and rereading your novels, your journalism, and your story A Christmas Carol, with its pointed message that a decent society depends on the rich learning to be generous and the poor being saved from ignorance and want.

We are talking about your heroes and your villains: Pecksniff, Squeers, Quilp, Murdstone, Headstone; your jokes and your pathos; your silly, pretty little women; your strong women – Betsey Trotwood, Peggotty – and your glorious comic women: Mrs Gamp, Mrs Todgers, Flora Finching.

We note your celebration of the strength and resilience of disabled people: Jenny Wren, whose body is twisted and painful and who makes her career as a dolls' dressmaker; Phil Squod, who can't walk straight and is disfigured, and who is hard-working, loyal and kind; Miss Flite, whose madness sees the truth; crazy Barnaby; hairless Maggie; Sloppy, whose head is too small.

We are enjoying the way you bring London to life before our eyes: streets, river, bridges, shops, dust heaps, markets, prisons. And we are reading your letters – more evidence of your unmatched reporter's eye – with their display of high spirits, enthusiasm, generosity and, it must be said, black temper at bad times.

Novels and letters give us a panoramic view of 19th-century England. But what would you make of the 21st century, the world of 2012?

In London, you would notice at once that the great black bulging dome of St Paul's, as you described it, is no longer black. The fog, the mud and the filthiest slums have gone. The absence of workhouses and the small number of street children would please you, and the lack of blatant prostitution in the Haymarket.

But you would see the same gulf between the rich, at ease enjoying their money and power, and the poor, relying on out-of-date food thrown out by supermarkets and food parcels from charities, and fearing for their jobs. And since you were obsessively interested in prisons all your life, you might be daunted by the huge increase in our prisons and number of prisoners.

A glance at the newspapers would tell you that your crooked financier, Mr Merdle, has many successors, and that Lord Decimus Tite Barnacle and his Etonian friends and relations are still running things.

The biggest human change to strike you must be that Britain is now a multilingual and multicultural society – something you might find hard to understand at first. But you would quickly see what rich material for novels this offers, and that it is being brilliantly worked by a great many writers.

Technological changes, too, you would take note of and investigate. With a sigh, you would learn about easy birth control, which could have allowed you to have no more than the three children you desired. Flying, too, which would have allowed you to travel to Australia, where you would have liked to go – another great subject for your pen.

Radio, television, cinema would all make instant appeal to you. You could be on Start the Week next Monday, on the television news today. Film producers will be calling on your mobile phone – but you will be wary, because you have always had to protect yourself from suppliants and admirers. Could you give up your famous quill pen and ink to toy with a computer? I guess you could.

You would certainly be pleased to see all of your books on sale in bookshops, and online. And to learn that we still have some libraries left, although they are under attack. You always spoke up for them, and we will ask for your support now.

How much we should like to call on you at your Wellington Street office – it's still standing – and take you for a convivial lunch, with good wine and even cigars, in a cheerful restaurant, summoning up some of your friends to join you, as they so often did on your birthday: John Forster, your biographer, the artists Maclise, Clarkson Stanfield and John Leech, the great actor Macready and the comic actor John Pritt Harley, Count D'Orsay, Wilkie Collins, and your loyal manager, George Dolby.

The ladies must come on separate days: Miss Coutts, Mrs Gaskell, invisible Nelly. But we might bring in Leo Tolstoy, who never met you but declared you the greatest novelist of the 19th century, and kept your portrait on his wall.

After which you could slip away (by helicopter?) to Gad's Hill and settle down with another cigar and some punch in the conservatory you built, specially decked out with the scarlet geraniums you liked best.

Mr Dickens, you are still, and always will be, the Inimitable. Many happy returns.

Claire Tomalin is the author of Charles Dickens: A Life, published by Viking. She will give a talk about Dickens at Southwark Cathedral at 6.30pm on Tuesday