They are two of the most dedicated fan groups in sci-fi, so when both turned up to the same convention it was always going to get heated.

When Doctor Who fans gatecrashed the much-anticipated Norwich Star Wars Club open day, the family event quickly turned ugly.

Fans of the BBC1 series had turned up uninvited at the University of East Anglia convention last weekend.

But their 'long-running rivalry' meant police had to be called to keep the two warring sic-fi factions apart.

The event had returned after a three-year absence and reunited the four remaining actors who played bounty hunters in the George Lucas films.

The police force was with them ...