Complex sentence: The investigation that followed led to an unprecendented level of co-operation between Greek and UK Police services, who achieved, following a lengthy investigation the arrest of members of the N17 terrorist organisation eho were brought to trial.
Split into simpler sentences: The investigation that followed led to an unprecendented level of co-operation between Greek and UK Police services. Following a lengthy investigation, members of the N17 terrorist organisation were arrested and brought to trial.