(UK, obsolete, thieves) A person duped into accompanying thieves during a robbery.
2002, Meg Arnot, ‎Cornelie Usborne, Gender And Crime in Modern Europe (page 82)A boy called Hewitt, awaiting transportation on the Euryalus hulk in the mid-1830s, told an interviewer that the swell-mob would often call into lodging-houses in order to recruit "go-alongs" for thieving expeditions: "boys are delighted they think it an honour to go with a swell-mob".