NOT many people today remember ET John, onetime Liberal MP for Denbigh. It was he who tabled the Bill for a Welsh Parliament in March 1914 in those last innocent months before the Great War and he was one of only three Welsh MPs to vote against the conscription Bill of 1916. He then joined the Labour Party but was never successfully re-elected. He killed himself in 1931.

During the latter years of the war and the few years after it, talk of home rule was again in the air. Cross-party conferences were held in Abertridwr, Llandrindod Wells and Newport and Westminster created two “Speakers’ conferences” on home rule.

But by the time Sir Robert Thomas, a Liberal MP for Wrexham, presented his Government of Wales Bill for a second reading on April 28, 1922, the subject and campaign was essentially dead.

So what went wrong for ET John and the home rulers? How was it that at a time when half a dozen new nation states were formed across Europe – countries like Estonia or Ireland, which were smaller and poorer than Wales – did Wales end up with nothing? Zilch. In fact, we saw a claw-back of devolution and increased centralisation in the 1920s and 1930s.

One lesson, among many, was the failure to create a mass movement for Home Rule, and another was for its supporters not to prioritise that movement above all others. Some form of Home Rule or, at least, recognition of Welsh nationality, had broad support in Wales, but it was academic, boring and seen as an added extra. Respectable, earnest conferences by polite people, of itself, didn’t deliver change. Respectable people who wish for citations with every point made can’t form a mass movement.

In 10 years’ time Wales will be either an independent nation state or it will be incorporated into England and Wales. That’s the logical dynamic of Brexit. Devolution will not hold. We are living in a flux not dissimilar to exactly a century ago – a crisis, again, centred around British nationalism and hubris.

We can’t afford to make the same mistakes as ET John again.

If Wales is to survive as a nation, and our communities to be stronger, we have to build a broad mass movement for independence. That is the job of YesCymru and this weekend’s All Under One Banner march in Merthyr.

We have to drag the national movement out of the cozy committee rooms and on to the streets. We have to appeal to the hearts of Welsh people with the same strategies as the British establishment does – colour, music, parades. We have to appeal to the minds with respectful, well-thought facts and answers. We also have to, and do, accept all people as they are. We don’t hold a measuring tape to people’s Welshness. In fact, you need not be Welsh, nor want to be Welsh, to be a supporter of an independent Wales. We want people, to paraphrase the words of Mark Darcy in Bridget Jones’s Diary, “as they are”.

Brexit was won partly through social media. But as people become more savvy to social media spin, they’ll expect to see movements backed up by real people. The march on Merthyr will give an opportunity for people to share and see happy images of real people they know, marching for a Wales independent of Westminster. They’ll see independence isn’t an astroturf campaign but one with real roots and real people and real communities. Soon, we’ll be demanding that the BBC give YesCymru a seat on the morning shows as they do unquestionably to dodgy groups like the Taxpayers’ Alliance. Why not?

ET John’s dream of a Welsh Parliament in the 1920s came to nothing; classic Westminster delaying tactics and the lack of a mass movement hampered it. And, ultimately, the formation of the Irish Free State in 1922 meant that the crisis of home rule for the Celtic countries was off the agenda.

The lesson for us in YesCymru a century later as we build up a mass grassroots campaign, and with independence achievable very soon in Scotland and Ireland, is we can’t afford to miss this opportunity. This is our last chance. Our movement is funded by membership and events. Our local groups organise street stalls, comedy gigs and barbecues. We’re working on more information giving the arguments for independence.

Someday soon, the independence question is going to land on the lap of the Welsh people and politicians whether they want it or not. Our job in YesCymru is to build as broad a movement as possible, with arguments already aired and discussed so that we can take the exciting vision of a Wales independent of Westminster, and a full part of the world, like our rugby and football teams, to the people.

In respect and memory of the decent people like ET John, we won’t fail.

Sion T Jobbins is chair of Yes Cymru