Verified answer

No - that is a SCAM. @london.com is a free email often used by scammers

If it doesn't end in .GOV.UK you are not dealing with the British government. All Home Office emails end in @ukba.gsi.gov.uk -- nothing else

Besides, work permits can only be applied for in YOUR country of legal residence through the British Embassy or their authorised visa agency. You cannot apply for this through the UK.

And if you were not flown to the UK for an actual interview, or did not interview IN PERSON with the employer's licensed recruitment agency then the job offer is a scam. No employer can get approved for a Certificate of Sponsorship unless they can prove the candidate has been extensively interviewed