There's a grove of trees on the pavement by the river, young enough that they feel almost like undergrowth but tall enough you don't get caught in their lower branches. Leading a path into them, after dark, is a wiggling and intermittent line of green lights, glowing up from the ground. At first, I thought that this, alone, was the memorial. If it had been, it would have been beautiful in itself. But no.

Half way in, ghosts start to appear through the night: that they are eight foot tall only highlights their vulnerability: they are emaciated, starving. Starving to death: a small group of the million who died in the potato famine, cast in cold metal on Dublin's riverside for all time. In the middle is a woman, holding in her hand a bouquet of real, wilting flowers, which must have been placed there in the last day or so. At the back, a man has a bundle over his shoulders: a small child, slack like a loosely packed sack, dead or soon to be.

Around the corner, on a traffic island, is the Amnesty memorial: a gas flame in a 10ft “barbed wire” ball “it's better to light a candle than curse the darkness”. It's covered in padlocks with, written on each, the name of a couple and a year: “Sean and Jenny, 2014”. On the same street is a statue of James Connolly with the inscription “The cause of labour is the cause of Ireland. The cause of Ireland is the cause of labour.” It's one of the few I can think of of a trade union leader. Not far away is the main station in the city, named for this Edinburgh born socialist and Irish republican, executed by the British state in the lifetime of my grandparents.

His predecessor as trade union leader in Dublin, the Liverpool born Jim Larkin, is commemorated in pride of place outside the central General Post Office. He's stood on a plinth, giving a speech to the bygone masses below, hands gesticulating, in full flow. I only know who he is because, in the National Library of Ireland, next to the parliament building, there is an exhibition of the 1913 lock-out. Larkin led thousands of Dublin's workers against their bosses after some had been sacked for union membership: the struggle which included the original “bloody Sunday”.

Big Jim Larkin at the GPO/Wikimedia

Further down the road is a statue of William Smith O'Brian who, it proudly pronounces, was sentenced to death for high treason. Beyond him, the O'Connell Statue commemorates “The Liberator”, Daniel O'Connell, a 19th Century Irish Radical MP who fought for Catholic emancipation and Irish independence. The GPO, past which these statues run, is still riddled with bullet holes from the 1916 Easter Rising. A cobble's throw from this crowd of proud socialists and revolutionaries lies the city's financial district, home to new rulers of the world.

Over three weeks, I visited each of the seven national capitals on this geological archipelago. In Cardiff, the main statue in the centre of town is of Nye Bevan – he of the NHS, who called the Tories “lower than vermin”. Otherwise, there are a good number of statues of ordinary people compared to most cities I've noticed: “girl” “miner” “mother and son” “people like us” - though, as with everywhere else, far too few of women.

Nye Bevan, Cardiff/wikimedia

In Edinburgh's St Andrew's Square, on top of a vast plinth, is a statue to Henry Dundas, 1st Viscount Melville: a key figure in the movement against the abolition of slavery, the last person in Britain to be impeached for misappropriation of public money, known in his time as “the Great Tyrant” because of his largely unaccountable grip on Scottish politics.

"The Great Tyrant"

Whilst Dundas is not the only ruler commemorated in Scotland's capital, the most consistent feature of the city's public art is writers and academics: Adam Smith; David Hume; the Scott monument - the biggest to an author on the planet; John Playfair; Dougal Stewart; Robert Burns (more than once); Robert Louis Stephenson and, separately, two of the characters he created in 'Kidnapped'; Arthur Conan Doyle; James Clerk Maxwell; William Chambers; Allan Ramsay; John Wilson; Adam Black; and James Young Simpson all have their likenesses carved somewhere in the city, whilst each of the university's buildings is named for an Enlightenment figure or other.

The most visited piece of public art in Scotland's capital is possibly “Greyfriars Bobby” - the dog who sat by his owners' grave for years. He's in the kirk-yard in which the Act of the Covenant was signed in blood, in one of Scotland's biggest ever civil rebellions, separating church and state for the first time in any Western country, but it's the story of canine loyalty, not human descent, which the powers that be have recorded for posterity.

David Balfour and Alan Breck Stewart from Kdnapped - Wikimedia

Hidden away in Princes Street gardens is a memorial to the Spanish Brigades – the men who went to Spain to fight fascists in the Civil War. On Festival Square there is a statue of a South African mother and child, erected in solidarity with the movement against apartheid and on top of Calton Hill is the Political Martyrs' Monument, commemorating five 18th and 19th century political reformers. But apart from that, unless you count a memorial and a statue to Burns, the city's radical past, and even the lives of working class people who lived there, are largely ignored. Perhaps the greatest act of public art rebellion comes in the form of a wrunckle on George IV's knee: the king had worn a kilt for the first royal visit to Scotland in 170 years, but added pink tights to hide himself from the cold, much to the mirth of the locals.

South African Mother and Child, Edinburgh - a rare statue of a woman

Truro has a 15ft high naked drummer, made from Cornish tin and copper, designed to symbolise Cornish culture. Douglas, capital of Mann, has one large monument to the Queen, a towering war memorial on the sea front, and a human size statue of late resident Norman Wisdom sitting on a bench.

Norman Wisdom statue, Douglas, Mann/manxscenes.com

In central Belfast there are surprisingly few statues. Scattered around their Queen outside the City Hall, there's a crowd of Victorian Mayors, Lords Mayors and MPs, and, alongside them, memorials to soldiers killed in various of Britain's wars over the years and in the Titianic disaster. Beyond that, the city is notable for its less specific public art: memorials to no one in particular in a land where details of history are not quibbles for academics but weapons of wars. Apparently there used to be many more statues, but the IRA went through a phase of blowing them up.

The Spirit of Belfast/Wikimedia

England doesn't have a capital - yet. Official London is profoundly British and the statues that command its vistas are mostly imperial, celebrating its rulers’ victories not the victims of their success. The most prominent statue as you arrive at the Houses of Parliament, for example, is of Oliver Cromwell: a man who led armies which murdered thousands of Irish civilians and who is one of the most hated names there. Last year, though, a plaque went up to commemorate Thomas Rainsborough, the Leveller and early democrat. There is hope...

Statues aren't the only way that cities shout about themselves. An Australian friend once commented that in London you see union flags, in England, you see English flags and in Edinburgh, you see Scottish and EU flags. That seems pretty much right, though in Edinburgh and London there aren't huge numbers of any of these compared to some other places.

I was amazed at the number of Cornish crosses that fluttered over Truro, but this was nothing to the Manx flags all across the island: every 25 paces down the waterfront in Douglas, every ten paces up the high street in Ramsey, and the three legged logo is on every inch of spare space. Cardiff, in contrast, has few of any colour and in Dublin, Cork and Galway, I counted more with the stripes of the rainbow than of the Republic. LGBT rights are contested. Being Irish isn't, so it's only the former that need to be asserted. In Belfast, a flag is enough to trigger a riot, and I didn't see a single one anywhere in the city centre. Travel out of town, though, to residential areas, and it's a different story...

The seafront on Douglas, Mann

Also interesting is what other nations flags are most often flown. Across all of these islands, Spain's symbol was the most common foreign insignia I spotted: presumably because a generation of migrants has now been here long enough to establish its own businesses. On the Isle of Man I found the most complete sets of flags of the nations of these islands and, on two occasions, found items displaying the signs of each of the Celtic countries – the same combination as the above, but swapping England for Brittany. Only twice, though, in hundreds of flags on this Crown Protectorate, did I see a union flag: once by the war memorial, once outside a bar called “The British”. By contrast, I counted the Cornish flag thrice. In Ireland, numerous pubs had a range of flags of home and foreign nations, but again, the Union flag and English flag were noticeable by their absence.

of flags of this archipelago - Douglas, Mann

Too often, public art fades into the background – when I told people on Mann that there are flags everywhere, most responded that they hadn't ever noticed. When I ask people in Edinburgh who's atop the St Andrews' Square plynth, the biggest in the city, they almost never know. But almost everywhere, you spot an ideology not by what is noticed, but by what goes unnoticed, not by what's there, but by what's not.

You can get Adam Ramsay's e-book "42 Reasons to Support Scottish Independence" here.