The UK has Europe’s biggest herd of unicorns—private companies that are valued at $1 billion or more. Part of how it got there was through funding from the European Investment Fund. But that source of EU venture capital could very well be cut off when Britain leaves the bloc.

The EIF is a public-private partnership that acts as a magnet, drawing private cash into funds it contributes to. In the UK, it has played a part in some 34% of later-stage venture capital investing (by value) in recent years, according to a consultation published this week by the Treasury. The UK’s own British Business Bank accounted for about 14% during that period.

There are signs (paywall) that the European fund, whose shareholders include the European Commission, has been slowing its UK investments even before the 2019 deadline for divorce. To make matters worse, small UK companies may have already been running short of capital.

That’s why the UK is looking to replace the EIF with its own version of a private-public partnership. But getting such a fund up and running takes time, and British firms could be starved of money in the meantime.

Last year the UK’s Autumn Statement, a budget statement the chancellor of the exchequer makes to parliament, included £400 million of new investment into venture capital funds during the next four years via the British Business Bank. This week’s Treasury consultation suggested Britain should be ready to replace the EIF and scrape up even more cash.

Britain is home to Europe’s biggest herd of unicorns, but it’s still far behind the US and China—perhaps too far behind, given its potential.

Even when adjusted for the size of their economies, British entrepreneurs don’t have as much access to capital as their American counterparts, with funding that falls about £4 billion ($5.3 billion) a year short of what they need to be as dynamic as US firms, according to the Treasury analysis.

A negative feedback loop may be at work, according to the Treasury: UK investments tend to produce lower returns than similar ones in the US. In turn, asset managers have been less focused on Britain and therefore develop less expertise in assessing British companies. Entrepreneurs starved of capital aren’t able to build and grow their companies, remain sub-scale, and risk remaining overlooked.

Since the Brexit vote, the UK has avoided some of the most dire predictions. Its economy is slowing but hasn’t collapsed, and its financial sector is bruised but not beaten. Likewise, there are signs that venture capital funding has held up so far. Still, the Treasury’s consultation demonstrates how much is at stake as Brexit negotiations play out. The unavoidable conclusion is the UK still has a lot to lose as it unravels itself from the EU.