Surely this can't be legal

[Emphasise]

DH's employers recently took on a female graduate in a technical/Engineering role. DH was impressed with what he saw fir first few weeks, then out of the blue, turned up at work to find she'd been sacked. Apparently, it had cone to light that her partner worked for the opposition.

I know she'll have no employment rights as she wasn't there long, but it still seems all kinds of wrong to me - to sack a woman because of who she lives with?

It's appalling, but if you're only there a short time they can sack you for antyhing they feel like.

Depends if she was asked to declare any conflict of interest and chose not to disclose. Think of the recent Bank of England case.

The way you've phrased your OP suggests you think the fact this employee was a woman might be relevant, is that the case?

I don't know if it's relevant flowery, but it feels like it might be. I dont know if anyone has ever asked dh what I do, for example.

When I started my new job last summer I had to declare whether a close family member worked for a competitor or for a company that my company could have contracts with. I imagine I would get sacked if it was found that I didn't disclose. It's common in certain industries, they have to avoid conflicts of interest, avoid accusations of favouritism when awarding contracts etc.

Your DH would probably have had to sign a similar declaration when he started.

As she has been with the company less than two years she can only take action if there has been discrimination.

If she is married to or in a civil relationship with her partner this could be discrimination. In Dunn v Institute of Cemetery and Crematorium Management the Employment Appeal Tribunal held that the protection against discrimination on grounds of marital status extended to discrimination due to being married to a particular person. However, if she is not married to or in a civil partnership with her partner the position is less clear.

It would be sex discrimination if male employees in this situation were not also dismissed.

If she had been with the company two years she would be able to take action for unfair dismissal. Her employer would have to show that there was a real risk of confidential information being disclosed to the competitor and that there was no alternative to dismissal. Even then it is by no means certain the employer would be able to convince a tribunal that this was a fair dismissal.