From SOAS, ride around the NW side of Russell Square and make for Bernard Street which is straight ahead, with a sign for Russell Square Station at the end of it. There is a cycle lane down the middle of the road guiding you there. Take the first right after the station (Grenville Street) and turn left into Guilford Street. After about 150 metres, you come to the gates of Coram's Fields Children's Playground.
For a shorter ride, skip to Section 3.