If you have never heard of 'boot sale app' Shpock, you might soon. The company is on the verge of a big, marketing-led push into the UK.

The concept is simple: “reinventing classified adverts for the smartphone generation”, as cofounder Armin Strbac puts it. He sees its main competitor as eBay.

trendingtopics.at © Jakob Steinschaden

Here's how it works for sellers: you take up to five photos of the item you want to get rid of, provide a brief description, then you are ready to sell.

For buyers, you scroll through an Instagram-style selection of items for sale, ranked from those closest to your location to furthest away. Users can ask questions or make an offer for the item, then the two parties can agree whether they want to transfer the goods in person or via post.

Shpock, which stands for 'shop in your pocket', was set up in Vienna in 2012 by Strbac and Katharina Klausberger. Strbac was previously a consultant at Boston Consulting Group while Klausberger worked at Vienna's Economics and Business University.

The company's 75 staff are based in the Austrian capital. It is available in six countries and the app has a big German user base. However, it is hoping to expand rapidly overseas, in particular in the UK, where it launched in 2014.

“We want to conquer the UK,” says Strbac. British users are different to others. They are very active and engaged... smartphone penetration is much higher in the UK than most other countries.”

It hosts some unusual items, such as Spice Girl Mel C's outfit from the 'Spiceworld' film, Russell Brand's shoes and Noel Gallagher's guitar, all of which will be sold for charity.

One person in the UK even posted an advert for a zebra (although this was taken down afterwards), according to Strbac, however it is typically used to sell fashion, electronics and items for the home and garden.

The app is the most popular shopping app in the Apple App Store and one of the top shopping apps in Google Play.

Strbac claims it has 10 million users. However, he admits this includes people who have merely visited the website (which gets 1.7 billion page impressions a month), rather than people who have actually bought or sold via the app. This makes it a somewhat unreliable figure.

And this isn't the only surprise. Last September, the cofounders sold a whopping 91 percent stake in their business to Norwegian media company Schibsted Classifieds, which valued Shpock at €200 million (£153 million).

Strbac won't say how much they invested in the company but local reports at the time say it was a 'seven digit sum'.

“We never disclosed total investment. We're not defining ourselves by how much we have raised as that doesn't say much about the company or users. We have been staying under the radar until now as that's proven quite successful for us,” says Strbac.

He denies the idea the cofounders have exited, however, on Schibsted's website it says it is 'taking over control' of Shpock.

Strbac says: “I don't have any lock in. If I am not happy with what the investor decides I could walk away immediately.”

However, again, Schibsted tells a different story. Its website states that “founders and key team members stay on board and will drive the development in the upcoming years”.

Another sticking point is how the startup will make money. Strbac suggests there could be advertisements within the app, or users could pay a fee to get their listings positioned more prominently. However, details are sketchy on this too.

The biggest challenge so far has been “organisational development”, he says. The hardest point came in the leap from 25 to 50 members of staff.

“Everybody has to be involved and up-to-date on what's happening. It was easy when there were 25 team members but when it's 35 or 50 that became more complex,” Strbac says.

“Every week is still a rollercoaster. The biggest lesson is to fully focus on the team and never compromise on team fit... every time we've thought someone who has been a bit of a pain might work eventually, they never have. The important thing is to succeed as a team,” he adds.

According to Strbac the biggest threat to Shpock is “not keeping up with tech development and the expectations of users... the biggest threat is to grow to a size where we can't keep up the speed”.

For an outsider it's very hard to judge Shpock's biggest threat. But it's easy to identify one weakness: secrecy.

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