Trying to diagnose my misfiring Series 3 Land Rover

My Series 3 Land Rover is not running smoothly and misfiring, so I will work my way through the ignition and fuel systems to try to find what's wrong - starting with testing the spark plugs and leads.
As you can tell, I'm not an expert, so advice is very welcome!

[@Grahame59]

So, plug No.1 is very black. You need to take out another plug and compare the two. If the other plug is not sooty then there is a problem with No.1 plug or lead, if both are sooty it's the fuel mixture.

[@Rich_Runs_Cars]

@Grahame59 Many thanks for the advice - the others are not so sooty. I'm thinking that I'll renew most of the ignition components and see how I get on - will order the parts shortly!