Tottenham Court Road Station is the closest station to the office on Denmark Street and right across the street from Strike’s favorite pub, The Tottenham. 

We first see Tottenham Court Road station in Career of Evil when Robin is on her way to work and later on when Strike is walking towards it. 

“The everlasting roadworks around Tottenham Court Road station had obstructed Robin’s walk to work ever since she had started at the private detective agency in Denmark Street.” Career of Evil, Chapter 2 

Below is an older shot of all the construction around the area:

We also see Robin use Tottenham Court Station a few times in Troubled Blood. 

Here is a more current picture without all the construction:  

Here’s a great shot of the station seen from inside The Tottenham.

Below is the walk from the station to the office on Denmark Street: 

Find Tottenham Court Road Station on the map below: