Questions about Beaufighters, thanks

Hello everyone, I'm the author of several novels including two involving the RFC and RAF during WW1 and WW2 respectively. I'm embarking on a new novel in which I'm hoping to include RAF Beaufighter operations based around Plymouth circa 1943-1944 ... please understand that the plotting and story arc is still very much in an early stage - that's a very broad description at this point and history likely clashes with my ambitions.
Researching the Beaufighter, I can see it had many roles and variants, but I have a somewhat basic question - what did the observer actually do? Some models had radar (a subject I'll be researching in more detail), I know, but as far as I can see, the Beaufighter was first designed before radar was an option ... so in general, if that makes sense, what did the observer do?
Thanks for any help. I realise this probably all sounds quite simplistic and uninformed, but these writing processes need to start somewhere!

Cheers, Graeme. (Author name G.M.Hague)

Navigator, Wireless Operator

Interior photos here, https://www.nationalmuseum.af.mil/V...s/Display/Article/196290/bristol-beaufighter/

Yes, navigation and radio communications but also lookout for enemy aircraft approaching from behind and rear defense when fitted with a gun.

Also, the earlier Beau Mk1 used drum-fed cannon, as shown in the photos in the previous link (changed to belt-fed in later variants, fed from tanks in the centre section).
It was the Observer's job to change these drums when required, not an easy task, especially if the aircraft was other than straight and level, as each loaded drum magazine weighed around 60 lbs !!

Thanks everyone! I've been researching like mad and as much as the Beaufighter's history appeals to me, it looks like my new novel would be better served based on Typhoon operations out of Harrowbeer (Plymouth). Bearing in mind that I'm writing fiction and won't be directly quoting real squadron histories, of course. But I can see a "cameo" from a Beaufighter in the story too.
Cheers again for your help.

The book "Beaufighter Boys" covers the actions of the GIB. For shipping strike missions he was charged with the responsibility of taking photos and he also had the job of changing out the ammo drums on the 20MM cannon, I think on all versions.

Cannon drum magazines only on the Mk1 (and I think also the Mk.II, Merlin engined).
Later Mks used belt-fed cannon, with the ammo in four tanks in the centre section.