Complex sentence: HM Customs and Excise officers also guard the borders of the United Kingdom from smugglers and illegal immigrants, although their duties in respect of people smuggling are to be transferred to the Serious Organised Crime Agency.
Split into simpler sentences: HM Customs and Excise officers guarded the borders of the United Kingdom from smugglers and illegal immigrants. The duties of HMCE in respect of people smuggling are to be transferred to the Serious Organised Crime Agency.