The register
The register lists ATN (UK) LTD in London as a licensed sponsor on Skilled Worker, an entry that goes back to at least 2026. Rating on the current register: Worker (A rating).
At Companies House the business is ATN(UK) LTD (company number 13105017), a private limited company incorporated in 2020, 5 years ago. The registered office is at Flat 14 Meadway Court, Meadway, London, NW11 6PN, NW11 6PN. Its filed activity puts it in professional and technical services.
Holding a licence is the expensive, slow part done. For ATN (UK) LTD the question each time is only whether the role and the pay fit the current rules, and that is checked per vacancy.