There is, you'll be surprised to hear, a Henry and Edward in all of us.

I'm breaking the news to you gently here. For the H and E of whom I speak are Dr Jekyll and Mr Hyde of that ilk. Yup, that was their first names. Kind of takes the sting out of the horror, don't you think?

I write in the wake of news Henry and Edward statues are to be plonked, if that is the architectural term, on Edinburgh's Royal Mile. They will commemorate the famous novella, The Strange Case of Dr Jekyll and Mr Hyde, by the capital's famous literary son, Robert Louis Stevenson.

In plans backed by the Unesco Edinburgh City of Literature and Edinburgh World Heritage trusts, new urban gardens on either side of the Lawnmarket will, if approved, provide habitats for the discombobulating duo.

When no one is looking, the pair might pop into nearby Deacon Brodie's Tavern, named after a character thought to have at least partly inspired Stevenson's tale. Brodie worked as a respectable burglar by night and a cunning councillor by day.

Not that Henry and Edward would ever get peace in the Lawnmarket to slope off for a swift half and half. The stretch of street at the top of the Mile is bustling and lively, certainly compared to the bottom half, which dies a death below St Mary's Street before being brought back to life briefly at the Scottish Parliament, where tourists from normal countries come to titter.

Thus Edinburgh, a city that does things by halves. Even one of its most famous streets has a split-personality. Stevenson's tale, published in 1886, reflected the hypocrisy of his age, where outward shows of upstanding morality masked visceral depravity.

Does that sound like the Edinburgh we all know and quite like? Oddly enough, The Strange Tale of Henry and Edward was written during an inspired few days in Bournemouth. Inspired by drugs, some say, as RLS was in a fever. Dorset has that effect on some people.

But it's unlikely to have inspired the novella. The supposed two-faced nature of Edinburgh is the more likely candidate. Edinburgh, as the bons mots have it, all fur coat and no underpants. Edinburgh, with its powdered face and its dirty behind.

A little uncharitable, I feel, though you may wish to add more charges: Edinburgh, with its rich-poor divide, the submerged, crowded Cowgate of Stevenson's day contrasted with the broad, prosperous avenues of the New Town. Today, you might compare the millionaires' mansions of the Grange with the peripheral cooncil estates. If you ever get lost, incidentally, you'll know you're in the Grange from the number of Labour posters in the windows.

But why shouldn't the rest of the country share the pain with its urban-rural, highland-lowland, Protestant-Catholic dichotomies? And that's before we get on to the independence-dependence split, with Dr Jekyll in Glasgow and Mr Hyde in Dumfriesshire.

All that said, it's not about nations and cities, but about the dark and light within us all, or within you at any rate. Before you start breaking up the furniture and foaming at the mouth (admittedly, a not uncommon reaction to this column), let me be clear I am not accusing you or your other half of dissociative identity disorder. That's split personality to you. And you as well.

Perhaps you see yourself more as a Sir Danvers Carew, the nice, innocent (apart from being an MP) old gent murdered by Hyde. Or, with your rational scepticism, you may see yourself as more of a Hastie Lanyon. And, yes, I accept I'm just saying these names so I can roll them round my tongue.

At any rate, we have come a long way - you and you and I - since our original discussion of two statues. I may say that these are just part of a wider plan to big up the Mile's literary status, it having been a hub of publishing and a host to other makars such as Burns, R, and Scott, Sir W of that ilk.

The urban gardens are also meant to help make the joint more pedestrian-friendly. Indeed, visitors to the city would be advised to ditch the car and come in by Dr Park and Mr Ride.

There's a choice of two buses: one to Respectable Street and one to Demonic Avenue. Don't worry about which to get. It's the same place.