During a recent police investigation, Chief Inspector Stone was interviewing five local villains to try and identify who stole Mrs Archer's cake from the mid-summers fayre. Below is a summary of their statements:

Arnold:  it wasn't Edward
         it was Brian

Brian:   it wasn't Charlie
         it wasn't Edward

Charlie: it was Edward
         it wasn't Arnold

Derek:   it was Charlie
         it was Brian

Edward:  it was Derek
         it wasn't Arnold

It was well known that each suspect told exactly one lie. Can you determine who stole the cake?