William Pentecost Marylebone.

[Ruskie]

I have located Little Prescott Street. It was difficult to track down as it's not marked on a lot of maps I have. It is actually just south of Little Alie Street.

Just north of the 'a' in Royal Mint Street on this map:
http://london1872.com/stanford37b.htm

It was a narrow alley running north/south along the path of the current Mansell Street, between the Goods Depots in the left hand map:
http://maps.nls.uk/geo/explore/sidebyside.cfm#zoom=18&lat=51.5108&lon=-0.0725&layers=176&right=BingHyb

Added: Am having trouble sending you the snip of the street name from the baptism register via PM. If you want to PM me your email address I can try emailing it to you.