Clearing Completed Workitems

[phillips, tim]

Dear All,
 
We're using a workflow based upon task TS00007869 in order to process
incoming invoices.
 
Late last week, we had a problem with the RFC user 'WF-BATCH'; the user had
somehow got locked.  What this meant was that loads of workitems were
processed, and theoretically completed, but, due to the problem with the
receiver, no termination event was raised meaning we have an inbox filled
with workitems that have already been processed.
 
Now the problem has been fixed, and newly completed workitems are now
disappearing, can someone suggest how to clear out the others?
 
I could write an ABAP to do this, or we could logically delete them all (but
I'd rather not for audit trail reasons).  There must be a standard SAP
way......mustn't there?
 
Regards,
 
Timbo