Law & Order UK - what happened to Bill Paterson & the other bloke?

[scampadoodle]

I didn't watch much of the last series (which was only on about a month ago?) & tuned in last night to find a bit of a cast change. Did anything happen plot-wise to get rid of the other two, and have these 2 new characters come from nowhere or are we supposed to pretend they've always been there...?

Bill Patterson's character was promoted and the other lawyer one had to leave as was involved in jury rigging or some other skullduggery!

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Ben Daniels' character James Steele had to defend against an 'abuse of process' charge for convicting the wrong man (which we're to infer was due to an assistant/lover, rather than Steele, hiding a piece of evidence injurious to the prosecution). Steele won his defense but resigned, feeling he would be a detriment to the office.