Image copyright Thinkstock Image caption The market for British strawberries is growing

Just the sight of a juicy, red strawberry on a bright green stalk conjures up English summertime, Wimbledon and afternoon tea.

And the market for British strawberries is growing. But if rules on who can come and work in the UK change following the vote to leave the European Union, who is going to pick them?

To pick a ripe strawberry, you don't just yank it. There's a special knack: a slight flick of the wrist to snap off the stem.

The pickers at Langdon Manor Farm in Kent are astonishingly quick at it. Their hands dart out, locating the ripe berries, and transfer them to a plastic crate, without their breaking step as they move along the rows of plants.

Image caption There's a knack to picking strawberries quickly and efficiently

Almost all of the 200 pickers are from Eastern Europe, with a right to work in any EU country. Most will return home in the autumn, but some, like Roxana Bertolon from Romania, have made the UK their home. She has been here for six years.

"I like it here," she says simply. "So I stayed." She now supervises a team of pickers.

If the UK decides to alter its policy towards foreign workers, farms such as this one could face quite an upheaval.

But Roxana isn't too worried.

"Maybe the rules will change," she shrugs. "I don't care."

Image caption Roxana Bertolon from Romania has been picking strawberries on the farm for six years

Members of her picking team are primarily concerned about the immediate fall in the value of the pound, which means they'll have less money to send home.

But changes to the rules on seasonal and migrant labour are a worry for their employer, farmer Alastair Brooks.

"I'm hoping sense prevails," he says.

"Because they're seasonal migrant workers, so they come, work and go home, I'm hoping a scheme will be put in place that will allow that to continue, without which we could have a very unsure future."

Hard work

The demand for soft fruit, such as strawberries, has grown rapidly in recent years and UK farmers have invested to step up production.

But without workers willing to live at the farm and put in long hours over the summer months, it's going to be hard to keep that up.

Image caption Strawberry farmer Alastair Brookes says his costs will rise following Brexit

When Roxana first came to work here aged 22, all the strawberries were grown on the ground. The work was back-breaking and slow.

Since then, with the help of EU funding, Alastair Brooks has invested in an irrigated table-top system and polytunnels to combat the unreliable British weather.

The work is easier. And the new National Living Wage means workers are guaranteed a higher basic income.

But work still starts at 05:30, six days a week. They break for lunch at 11:00 and continue picking until around 13:00.

After that there's maintenance work, such as fixing irrigation systems and tidying up plants, that needs to be done.

Image caption Working on the farm means starting at 05:30, six days a week

The rest of the team packs the day's harvest into plastic containers, for labelling and shipping, to hit supermarket shelves by the next morning.

Still needed

So far, unemployed people in the UK have proven reluctant to take on these jobs.

"The English don't like to work like us," says Roxana. "They will never come to work on a farm.

"If they come, they want to be someone high [up], to be a supervisor or a manager, but not to pick."

Forklift truck team leader Andis Ivkins agrees. "I don't believe they'll send us home," he says. "I don't believe the English people will come and pick fruit."

He is from Latvia and his wife is from Lithuania. His face lights up as he explains they are about to have their first baby.

Image caption "I don't believe the English will come and pick fruit," says Latvian Andis Ivkins

Their plan is to stay in the UK for the next few years, and he doesn't see any need to change that plan, because he thinks people like him will still be needed on the farm.

But he's not certain the seasonal workers, who come and go each year, will keep coming.

If they're told to fill in extra paperwork and apply for visas, or are restricted by quotas, they may end up going to other European countries instead: perhaps Spain, the Netherlands or France. Especially if the pound remains weak.

Some recruitment agencies have already said interest is lower than usual following the referendum.

"Why would you come here if the message is you're not welcome?" says Laurence Olins, chairman of the industry association, British Summer Fruits.

"Europe is a big place. They don't have to come here. We're competing in a global market for labour. It's a very mobile resource."

Image caption Robots might eventually replace humans, but right now they are not as good at picking fruit

Mr Olins says the litmus test will be in October and November this year, when farmers start recruiting for next year's season. But he thinks there's going to be a "fight for labour".

Unclear future

Langdon Manor Farm faces other uncertainties, too.

Alastair expects his input costs to rise. The flourishing plants at Langdon Manor started life in Dutch greenhouses and Spanish nurseries.

The plastic for the polytunnels and the coir matting are also imported via the EU. With a weaker pound, all of those will be more expensive.

He expects to lose the financial support he's been getting from the EU, while rival European producers will continue to receive it.

Recently, he has had EU funding to explore the use of robotics on the farm. It is focusing initially on spraying, stacking crates and transporting the fruit from the field to the pack house.

Image caption British farmers expect to lose their EU funding, while their European rivals will still receive it

Robots are not very good at actually picking fruit, he says.

"If there's a leaf in the way, the robots can't see it. They go past, whereas we, as humans, have the intelligence to move the leaf."

So he's not planning on mechanising the harvesting. Not yet, anyway. But in the long run, he's not ruling it out.