(2-part post):
Questions about cautions come up almost daily on AB. It can be difficult to provide a definitive answer because there is no single definition of what a 'criminal record' is.
Historically (i.e. before cautions were introduced) someone was only considered to have a criminal record if they'd been convicted of an offence before a court. When cautions were first introduced, it was made clear that a caution is not a conviction and, therefore, does not create (or add to) a criminal record.
However, the CRB's records do show cautions which (since they show up on CRB checks) effectively makes them part of a (stricter) criminal record even if they don't 'officially' count.
The situation is further complicated by the fact that (since they're not convictions) there is no provision, under the Rehabilitation of Offenders Act, for cautions to become spent. Police forces may delete cautions from their records after a certain time, but there is no legal requirement for them to do so.