If you’ve seen one trade unionist on social media, it’s probably been Dave Ward, the 58-year-old boss of the Communication Workers’ Union. His Twitter account turns popular memes into political ones: during the election, a particularly successful series riffed on the “You versus the guy she told you not to worry about” meme, comparing the crowds greeting Jeremy Corbyn as he toured the country versus the controlled environments that Theresa May prepared to campaign in.

Ward’s use of social media, which he credits to his team, particularly Chris Webb, his communications director who sits in on our interview, came about when he was standing for general secretary. He was standing against Billy Hayes, the incumbent, and “when you take on an incumbent, they have control of [union] communications.”

“I'm not saying this is wrong,” he adds, “The union needs to keep communicating about industry issues or political issues, but because they've got a grip on that, we knew we needed to have something different.”

Ward, who started working at the Post Office aged 16, wasn’t “one of those people who got into politics having read stuff, it’s more instinctive to me”. He got involved in the union, after a union rep intervened when he had difficulties with his then-manager. “I thought, well, thanks very much, and I took an interest in the union then, and the comradeship.” There followed what he dubs a “long apprenticeship” as a workplace rep from 1978 onwards, until he became deputy general secretary in 2003.

But when he ran for general secretary in 2015, few expected him to win. His campaign held Q&As on Facebook, and, Ward recalls, “it just took off”. Much to the surprise of others in the labour movement and the parliamentary party, Ward won – and was immediately thrust into the hyper-political world of a Labour leadership contest.

He recognised in Corbyn a kindred spirit. “When Corbyn was talking about a different kind of politics,” he says, “the truth is we were talking privately about a different type of trade unionism”. The CWU was the first of Labour’s big unions to back Corbyn’s 2015 bid and one of the most enthusiastic, though they don’t always agree: Ward, a south Londoner, supports Chelsea, while Corbyn is a follower of Arsenal. “I told Jeremy: you can have that one,” he recalls of Arsenal’s 2-1 defeat of Chelsea in the FA Cup Final on 27 May.

“Our reason for supporting Jeremy initially,” Ward recalls, “was how poor, frankly, New Labour had been in defending our industry.”

Ward’s endorsement, which said that Corbyn would clear Labour of its “Blairite virus”, drew attention at the time and a rebuke from one of Ward’s predecessors at the CWU, Alan Johnson, who wrote in the Guardian: “I’ve known Ward for 25 years, during which he has never been a political activist. His interest was always firmly on the industrial side of the CWU. The sad thing is that he obviously felt that the only way he could attract attention as a newly elected general secretary was to slag off the Labour Party. In this respect he was following the example of some other leaders of affiliated unions whose only emotion when talking about Labour seems to be anger, the only volume setting loud.”

Unsurprisingly, Ward has a different interpretation of what drove his endorsement: his own memories of working with the Labour government as a union official. “The reality is Labour put forward a proposal to privatise [the Royal Mail] just before they went out of power, and they also put forward a liberalisation agenda, a competition agenda, that's exploiting terms and conditions, to come in without any protection for workers,” he argues.

I ask him if the other leaders of Labour’s major trade unions, some of whom came to support Corbyn slightly later down the line, ever expressed similar views to Johnson.

“Were there meetings where people were unsure [about Corbyn]?” he asks, “Yeah, of course. You've got to be honest about that as well. Some of that was perhaps legit. Not for the campaign. Obviously for the leadership contest, the first leadership contest there was pretty much, amongst the key union leaders, pretty much unanimous support in the end.”

By the second year, things looked more difficult. “It was clear to me that Jeremy himself didn't command the level of support amongst trade union leaders that he had done previously but I think everyone knows that. It’s no secret that people were positioning [for a leadership contest after an expected heavy defeat].”

I ask him what Corbyn needs to go one better, after his success last month, and take power. “Time,” Ward says without hesitation. “Just time.”

Warming to his theme, he says: “I don't think we need to overplay our hand. I think we need to keep doing what we've been doing, developing policy, getting out and building that movement. Continue to engage, and keep building on your policies. I think the economic stuff needs to come to the fore a bit. I think John McDonnell needs to be given a few platforms.

“I wouldn't personally, as a personal view, I wouldn't get preoccupied with how can we turn the situation where we haven't quite won, into bringing down a Tory minority government. Politics will take care of that, and there will be opportunities along the way to expose how weak that government is, I'm sure.”

But there is another aspect to how Labour can take power that will preoccupy him more: “What are we [the trade union movement] going to do? Jeremy's done a fantastic job. Those around him in the leadership team in Labour, and I think Momentum deserve a lot of credit, they've done a great job. And I'm sitting here now going, what am I going to do as a trade union leader? I'm not going to ride in on their shirttails. We have a responsibility as a trade union movement to do our bit.”

He thinks that trade unions have tended to focus too heavily on politics, particularly foreign policy, in recent years. Although he talks up the “fantastic people” at the TUC, he points out that “if I got all the [TUC] papers that I'd read, I'd have a pile like that on Brexit”, he holds up one hand very high, “and I'd have a pile like that on the world of work”. He holds up the other hand, much closer to the ground.

“I think we got political almost as an excuse for not being in the workplace,” he tells me, “and not influencing that change, because that became too difficult.”

Instead of trying to get a million people out on the streets to protest the Conservative government, he hopes to get “a million people out on the streets for a better deal for workers in this country, and to focus on the future world of work.”

What does the future look like? The picture he paints is not a happy one. “If we don't change the balance of forces, four or five companies in the world are going to gain huge power, financially, economically, politically.”

That’s why for Ward, his early endorsement of Corbyn is already paying dividends. “We thought that Labour needed fundamental change, and we saw Corbyn as the catalyst for that. I think what's fantastic now is he's delivered that in the Labour Party, and he's now become the catalyst for change in the political forces in the country.”