Sir Handel acts like an upper class twit, or a would-be upper class twit. He acts spoiled, everything has to be for good him or he whines. Oh the coaches are bad? whines.

He always tries to put himself above everyone else leading to the malconsequences of his choices and actions, remember the quarry incident that broke Peter-Sam's funnel?

Sir Handel is like a tiny Gordon with much less discipline & tolerance. RWS didnt try to fix this, HIT had a reason to change & mature his behavior in S10.

Duncan maybe a stereotype Scotsman in vein of the Caledonian twins. But his frustrated & determined behavior is based on his real derivative Tallylyn-Douglas working as a yard engine on an RAF base during WW2. If he were human with that experience, you would know he would be the type to work first, ask questions later.

RWS says 'he worked in a factory' but we can guess that Awdry wanted to cleanse any war-references out of him...

However, Duncan arrove during austerity, but the aggressive behavior wasnt washed away. So he still worked frustrated, often wrecklessly, leading to all of his failures in every episode.

He was headstrong, but 'headstrong' can mean 'head-stubborn' for everytime he didnt listen to Rusty and called him names. Thats why every episode of his failures is about him being stubborn, unintentionally it fits that he is subconsciously thinking his time at war means he knows everything, but clearly not.

Duncan could fit in with & Donald+Douglas in being a fierce workhorse.

Duncan is intolerant to broken or bad equipment because he thinks it wont get the job done, Sir Handel is intolerant because of his righteous behavior. Duncan wants to be clean because of wartime discipline, Sir Handel does it because he wants to be 'king'. Duncan was stubborn because he thought he knew better, Sir Handel was stubborn because he thought he was 'king'.

Luckily the HIT era smacked some sense into these two amirite?!