Simon Marcus is a political commentator and private investor, co-founder of the Boxing Academy, and contested Hampstead and Kilburn in 2015.

Too many Tories have failed to grasp the most important lesson from the election. We all know it was a poor campaign and Theresa May performed badly.

But the game changer, that too few are talking about, was Labour’s grassroots campaign machine. which deployed vast numbers of volunteers around the country – outnumbering the Conservatives ten to one in some seats.

This was the critical factor in Labour’s shock performance and, even with a competent campaign in the next election, the Conservatives must match Labour’s army of helpers to win.

This was why seats like Kensington fell, Peterborough was easy meat, Chester is no longer a marginal, and we lost Canterbury for the first time in 99 years. Also, there are now 28 seats where the Tories have less than a 2,000 majority over Labour.

So what’s going on? Corbyn’s hard-left message brings in hard-line activists. Tories don’t dream of revolution and utopia. We know it doesn’t work. The hard left do, its what they get out of bed for and why they work bloody hard.

Their militant zeal is frightening. As a PPC in Hampstead and Kilburn in 2015 I was near top of the marginal seat campaigns for attracting volunteers and gaining pledges. But no matter how many volunteers knocked on doors, Labour had double.

Since 2015 Labour membership itself has doubled, to around 500,000 in May 2017. But crucially the ‘Momentum’ organisation, Corbyn’s hard-left support group, now has 27,000 members with 200,000 ‘supporters’. Growing out of Corbyn’s 2015 leadership campaign, they were able to unite those with hard left views under one banner.

Whether the Socialist Workers Party, trade unions or Labour voters, ‘Momentum’ bought thousands of potential activists together, built huge databases, and mobilised them. They are now doing to the country what they did to Labour.

They developed their use of social media and IT to marshal their workers, and this approach has also been incorporated into mainstream Labour. A ‘phone banking’ app called ‘Grassroots Now,’ a carpooling app, and other pooling sites such as ‘mynearestmarginal,’ used by 100,000 people, helped activists work together and travel to where they were needed. It’s the old military adage: ‘get there first with the most.’

So on 8th June, Labour were able to put hundreds of activists into key seats where the Tories had 20 or 30 helpers. In Hampstead and Kilburn, Labour had ‘knocked up’ all their potential voters at least twice before 3pm. They did it again after 7pm.

That could be as many as 300 volunteers. There are no specific figures, but talking to various campaigners I would estimate that on polling day, the Conservatives had between 10,000 and 15,000 activists on the ground. Labour had over 70,000.

That is why the polls were wrong. Because most pollsters only counted those ‘certain to vote.’ Labour’s ground army found the uncertain voters and dragged them out. Smart social media is great, but it must be exploited by people who knock on your door, remind you what you think, and tell you where the polling station is.

The nearest we had to a mobile ground army was the ‘Road Trip 2015’ campaign, where around 50 volunteers were bussed to a marginal seat for a day, spurred on with the promise of food, drink, and sometimes hotels. Its great that people gave their time and it helped, but I heard stories of volunteers doing just a few hours leafleting before going to the pub, or constituencies that weren’t prepared for 50 activists.

Labour will double our two-hour sessions and won’t expect much of a reward. They will also canvass more than leaflet, when many Tories simply don’t like speaking to people on the doorstep. I remember the local elections in Camden, when one Saturday about 30 young campaigners turned up. I was impressed until I walked past half an hour later and they were still standing around talking to each other.

Some might claim the Tories have more volunteers than I state, but in the 2015 election I was sent lists of thousands. We called them all several times: most weren’t interested, some didn’t know why they were on the list, and several were deceased.

The Tory party has around 140,000 members, and most are not active. Labour have three times that. Their ‘blitzkrieg’ campaigning model is hard sell, face to face on the doorstep, and with good follow up. It can be deployed anywhere, win over undecided and new voters, and proved me wrong in bringing back ‘old Labour’ voters too.

Next time the Tories may have a better manifesto, a Prime Minister that is easier to sell, and a better campaign. Labour tactics will also find their limit in older, wealthier, rural areas. But with evenly matched campaigns, can Labour’s massive advantage in numbers overturn a 2,000 vote majority in 28 Tory seats? Yes, maybe more.

Labour are inspired, their numbers are rising – and yet too many Tories are in denial. Of course we need to worry about better social media, appealing to younger, more diverse voters, and re-packaging austerity. But even with the dreadful campaign we saw if we’d had half Labour’s ground army, well-led, we would have saved seats like Ipswich or Crewe and Nantwich.

The truth is no party can sustain electoral success when massively outnumbered on the ground. So the Conservtives can accept the challenge, recruit and train thousands of volunteers for the doorstep, and build a machine to match Labour, or they can settle for another minority government, or worse.