A gender-fluid worker has won an employment tribunal against Jaguar Land Rover (JLR).
Ms R Taylor brought claims against the company, saying she had suffered abuse and a lack of support.
She successfully argued she suffered harassment and discrimination because of gender reassignment.
In a statement, JLR apologised to Ms Taylor for her experiences during her employment and said it continued to strive to improve in this area.
Ms Taylor had worked at the company for almost 20 years as an engineer and had previously presented as male, said her barrister Robin White.
The JLR employee began identifying as gender fluid in 2017.
She then usually dressed in women's clothing and was subsequently subjected to insults from colleagues and abusive jokes at work, said Ms White.
Ms Taylor also suffered difficulties using toilet facilities and getting managerial support, the lawyer added.
After resigning in 2018, Ms Taylor took JLR to a tribunal arguing she had suffered harassment and direct discrimination in the workplace because of gender reassignment and sexual orientation.
She also claimed victimisation after the company later failed to permit her to retract her resignation.
Ms White said JLR had argued Ms Taylor, as gender fluid or non-binary, did not fall within the definition of a person who had undergone gender reassignment, a protected characteristic under the Equality Act (2010).
The tribunal panel found in Ms Taylor's favour after her lawyer argued the government itself referred to a gender "spectrum" during parliamentary debates about the Act.
A hearing on 2 October is set to decide what compensation the claimant will get.
Analysis - Ben Hunte: BBC LGBT Correspondent
While Jaguar Land Rover could still appeal the decision, this employment tribunal is being called a "milestone moment".
It shows that people with more complex gender identities can be protected from discrimination under the Equality Act.
While some people will be shocked that this was not already the case, one legal expert told me our laws "have not developed as quickly as society's understanding of sexual orientation and gender identity".
It is these blurred legal lines that have led to some trans people being confused about what rights they actually have, including non-binary people who are not currently legally recognised in the UK.
The BBC has spoken to several trans people who stayed silent about the transphobic abuse they were subjected to at work. Some trans workers were spat at by colleagues because of their choices of clothing, others were continually misgendered, and many were eventually forced out of their jobs.
For now, many people will be waiting on the longer explanation from this employment tribunal to understand more about why non-binary and gender-fluid identities now fall within the scope of the Equality Act.
In its judgement made on 14 September, the tribunal said it found it appropriate to award "aggravated damages" because of the "egregious way" the claimant was treated and because of the "insensitive stance" taken by JLR in defending proceedings. It also recommended the company takes "positive steps to avoid this situation arising again".
The claimant's compensation would also be increased by 20%, it said, because of JLR's failure to comply with the ACAS Code of Practice over Ms Taylor's grievance about measures to assist her transitioning.
Ms White said the ruling was important to her, not only as it broke "a little new legal ground", but because she had herself transitioned from male to female while practising as a barrister.
"I am immensely pleased for my client to have the result we have. I am also pleased with what we appear to have done to show protection applies to extra people who last week might not have thought they were protected in that way," she said.
Ms Taylor is now employed as an engineer with another company and "looking forward to getting on with life," Ms White said.
Dave Williams, JLR's Executive Director of HR, said: "On behalf of Jaguar Land Rover, I would like to apologise to Ms Taylor for the experiences she had during her employment with us.
"We continue to strive to improve in this area and we respect the outcome of the case."