There isn't a Residents' Association covering the lower part of St James's Park; the St James' Park Cul-de-Sac Residents' Association (formerly known as the St James' Park Residents' Association) covers the upper portion of the street only. There is interest in forming an Association in Northampton Street, which could include us (the minimum recommended size for a RA is 50 households).
The website of the Lansdown Cresent RA includes a page about their own Neighbourhood Watch, which sometimes carries local alerts about suspicious activity in the area. There is also useful local information on the websites for the Associations covering St James's Square, Circus Area and Marlborough Lane.