Either this is an AirBnB that needs a license for more than 90 days a year. Or it’s an AST tenancy since the landlady lives abroad and she needs to comply with all the laws around that.
No way could the person renting the room be said to be a lodger when the landlady doesn’t live there.
Isn’t there also a law about a tenant needing to withhold some of the rent when the landlord lives overseas, until the landlord confirms they are paying the correct tax?
Also, £1700 a month and it’s in Catford, there isn’t even a bedroom, a bed, or any bedding!:
https://m.spareroom.co.uk/flatshare/london/catford/3042043