The UK tech sector is one of the most vocal opponents of Brexit and chief among its concerns is the shrinking talent pool on tap.
Just three percent of tech professionals supported Britain leaving the EU according to a Tech London Advocates survey published shortly before the referendum.
Changes to EU funding, the economic impact, flow of trade and changes in regulation and legislation are all areas of concern, but the overriding fear is over the end of free movement of labour.
The worries are exacerbated by a dire shortage of digital skills in programming and statistical analysis as well as emerging areas like machine learning. Foreign talent is helping to fill a gap that a 'hard Brexit' only threatens to widen.
"There are questions about whether it will produce more skills shortages because fewer people will be attracted to the UK and it is likely to be harder to bring in enough people," says Naomi Hanrahan-Soar, who specialises in tech and immigration law and is a senior associate at London firm Lewis Silkin.
"Whatever new system we have, it is likely people will need to qualify in some way so that will necessarily incur either professional fees for assessing it and/or government fees for applying for it."
Future immigration policy remains unclear, but the days of the EU's 500 million citizens joining UK companies without a VISA will almost certainly be over.
Visa rules for tech
The likes of Facebook and Google have demonstrated their commitment to Britain after Brexit by opening huge new offices in the capital and promising to create thousands of jobs, but the vote has already had an impact on recruitment in the sector.
A third of tech founders reported they had already lost out on potential international hires due to Brexit, according to a survey released by Tech London Advocates in November 2017.
"The law isn't what's driving the change right now," says Hanrahan-Soar, who also serves as vice chair of techUK's skills, talent and migration group.
"The main effect that we're starting to see now is people being deterred. When you look at migration statistics, net migration has dropped significantly, but that's not because of any legal changes yet because the law hasn't changed."
The Tech London Advocates research was released a day after the government announced that it would double the number of visas available to highly skilled tech workers from outside the EU to 2,000.
This 'Tier 1 (Exceptional Talent) visa' has been granted sparingly in the past but applications have surged since the Brexit vote. Tech City UK said that 260 were endorsed in the last fiscal year, quadruple the number granted in the previous one.
The visa opens up the borders to talented tech workers who lack the resources for a Entrepreneur visa or Tier 1 Investor visa, which require access to £200,000 and £2,000,000 respectively. The problem for applicants is that wealth like this is the easiest way to demonstrate their talent.
"It's very difficult to prove exceptional talent until you are really successful, so until you've actually started your own business that's shown a really hefty turnover, by which point you probably just about qualify for some of those investment visas," says Hanrahan-Soar.
"They have increased the number so that they can approve more, but it's a question of how you really assess that. If you just think of that as a practical question, it can be quite difficult."
Objective assessments of an individual's talent are hard to make, as problems with the old Highly Skilled Migrants visa showed.
The visa was established to make an objective assessment of an applicant's merits by adding up earnings, level of education and age to reach a total number of points, but the system was exploited to fill roles for which it wasn't intended.
A secretary, for example, could meet the threshold for the visa if they had a high salary, a bachelor's degree and were under the age of 30.
Applicants for the current Exceptional Talent visa for the tech sector encounter their own obstacles to objectivity, such as the difficulty of understanding the role of an individual in the achievements of a team.
"It depends fundamentally on whether you trust the people making the decisions to make a subjective decision, because I don't think that there's any obvious way to make an objective decision," says Hanrahan-Soar.
What can change?
Hanrahan-Soar believes that it would be more useful to ease the current restrictions than offer more Exceptional Talent visas.
She argues that the government's efforts to deter employers from hiring foreign nationals have already gone too far. The legislation is incredibly complicated to navigate and raises bureaucratic and financial hurdles, such as a minimum income threshold of £18,600 for non-European spouses of British nationals.
"To give you an idea, if you're trying to bring just one foreign national to the UK for a five-year term so that they can reach the point of applying for indefinite leave to remain, it's going to cost the employer close to £10,000 just for the government fees before they've incurred anything else," says Hanrahan-Soar.
"People don't tend to try to hire foreign nationals to undercut the local labour market, because it tends to actually be more expensive and they tend to be hiring very skilled workers when you're talking the tech industry. Tech doesn't use low-skilled foreign labour the way that say fruit-picking does."
Businesses will likely only go through the cost and hassle of obtaining visas if the recruit is truly worth it.
Hanrahan-Soar thinks they should have more power to self-certify which foreign workers they can take, rather than meet the arbitrary thresholds of protracted and expensive applications.
Chief among the barriers she wants raised is the resident labour market test. This requires companies to advertise any job you're offering if it's not on the shortage occupation list for a lengthy period of time.
"If they're going through the process of getting a visa - which is going to take them something like two months - once they've used this resident open market test, they've already tested the market," she explains.
"Why bother wasting everybody's time with a lot of administrative hassle? I think that would be one of the most practical steps, to remove the resident labour market test."
How startups can attract foreign talent
The UK's talent, educational institutions, history of business and culture of innovation still make the country a big draw for tech talent. In 2017, a record £3 billion in venture capital funding was invested in Britain's tech sector, almost double the previous year's figure of £1.63 billion.
Tech remains the UK's fastest-growing industry for now, but its future prospects are heavily reliant on international collaboration and access to the best talent.
The current sentiment of foreign workers suggests their numbers could dramatically decline. In July 2017, 48 percent of migrant workers surveyed by Deloitte said the country had become less attractive as a result of Brexit.
Among highly skilled workers that figure rose to 65 percent of those from EU nations, and 49 percent among those from outside the EU.
Hanrahan-Soar says the tech sector should tell its positive immigration story to raise support of the public and the government.
Britain's thriving startup scene owes a great debt to immigration.
Nine of the 10 unicorns in analysis firm Zirra's list of the highest-valued UK startups have at least one non-native or child born to a first-generation immigrant in the founding team.
Opponents of free movement often focus on low-skilled workers being undercut by cheaper foreign labour, but this is not the common form of immigration in the tech sector.
The mobile nature of the tech sector also makes it an industry that can thrive outside the capital.
"For stimulating the economy outside of London, one of the UK's problems, tech is probably one of the best industries at doing that," says Hanrahan-Soar.
"It is the most capable of having people work from home and it's the least bound to London specifically."
She adds that despite widespread reports around tech's diversity problem, the sector can offer employment opportunities to people from all backgrounds, as it needs ideas from every background to create solutions to different problems.
"Tech companies could have their own media campaigns that counterbalance the anti-immigration campaign," she says.
"The reduction in net migration numbers since the referendum is the strongest evidence that we have that it's not the law that's making people not come to the UK, it's how much they perceive themselves as welcome. It's a cultural thing far more than a legal thing."