Extremely vulnerable wants to restart work

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Employer here, looking for opinions/advice please.
We originally furloughed approx 70% of staff. Fortunately everyone has been supportive and it's been a lifeline for us. Part of the business can now reopen and we are gradually asking people back.
A long standing employee received a letter from the NHS advising they stay at home and shield for 12 weeks. The medication they take classes them as extremely vulnerable although to all intents and purposes they are 'well' and their condition hasn't affected their ability to work.
They want to come back to work. While we can provide a safe environment I'm not sure of the legalities and would actually prefer they stay on furlough until the next government review. I would hate them to become ill simply because they returned to work.
Has anyone had similar circumstances? Thanks in advance.

Hello, different circumstances here as we are a large public sector employer so haven't been furloughing anyone, but we have been very clear that shielded staff must stay off work, however much they want to come in. Even if the work environment is safe and they are well, it is simply too much of a risk for these staff to come in. So I would advise this person needs to remain at home for at least a few weeks more, until the end of the 12 week period they were advised, and review what the government/health advice is then. Is there any work they could be doing at home in the meantime if you provide a laptop or other equipment?

For staff who are vulnerable but not shielded, pregnant, over 70, other health conditions, we are making detailed risk assessments with our Occupational Health service to see how/when it will be safe for them to come back but again the preference is that they stay at home where possible... we are lucky in that the majority of our staff can do at least some work from home, not sure how this is for your business?

Thanks maxelly, I really appreciate your comments.
Unfortunately working from home just isn't an option (think retail and gardens!) and after the government review last night I think we will be saying stay at home. Hopefully it won't be for too much longer.
Thanks again!