6 Oxford Street, London
The Tottenham is the public house to which Cormoran Strike went for lunch after taking on the CC:Lula Landrey case.
The Tottenham, as the name suggests, is located opposite Tottenham Court Road Tube station, on Oxford Street about 100m from the corner with Tottenham Court Road. As its signage proudly proclaims, it is the only pub on Oxford Street.
If you want to see this pub on Google Maps, a search for tottenham pub will fail; it will give you pubs in the London district of Tottenham, several miles away. The correct search is "The Tottenham" pub (including the quotes).