The source, who wishes to remain anonymous, said the inmate had been transferred to another jail since last Wednesday`s attack.
The Ministry of Justice confirmed that police were investigating the assault.
The source expressed concerns about staffing at the category C prison, echoing the findings of a report last year.
"Out of anyone, you would have thought there would have been people around who would have been able to get him away quickly."
Mr Cawkwell, who has held a number of senior positions in the prison service, has received hospital treatment for his injuries.
A prison service spokesman said it did not tolerate violence against staff and would "push for the strongest possible punishment".
In its last annual report, Wayland`s Independent Monitoring Board said it was concerned about staffing at the prison citing "staff shortages of up to 22%".
Vice chairman Roger Marston said the board was due to publish its latest report soon and that "a huge amount had been done in terms of recruitment and we have a full complement of staff."
He added that although not huge, there had been an increase in violence at the jail this year.
However, there have been a number of reports of disruptions at HMP Wayland this year.
In May, about 20 inmates were involved in a "food fight" which broke out during lunch, while two inmates attempted to grab keys from officers in a separate incident in June.
Another HMP Wayland inmate was jailed in June for an assault on two guards, during which one was bitten, according to police.
