"The book argues that debt has typically retained its primacy, with cash and barter usually limited to situations of low trust involving strangers or those not considered credit-worthy"
It would make sense that cash would pop up once the Romans arrived, and would be in small amounts to facilitate spot transactions between Romans and the pre-Roman peoples of Britain and why there's such little amounts of cash.
Further more, I can imagine a scenario where Roman coins were melted down to make these coins (total conjecture) .
Further more, I can imagine a scenario where Roman coins were melted down to make these coins (total conjecture) .