To a certain extend, explaining does work with ds2 ie at least he knows why the answer is Yes or No. But if he has decided to kick of, that will not stop him (he is much to stubborn for that )
For the story of the hat, for a change I had nothing to do with it! ds1 choose his hat, ds2 saw and took it out of his hands. ds1 said 'Nooo' and that was it really. ds2 has a hat of his own so not an issue of 'he has one and I don't'. Hence the fact I did carry him, rugby ball style, his back towards me to the school (thanksfully it's not too far). Didn't stop him screaming though or make him calm down or change his attitude (ie similar situation happened two days later about another object).

I agree about THE thing that will work. It's just that I haven't found it (or the one I have found doesn't sound very appealing). So if any suggestion is welcome

Hmmm, explaining things has no effect on mine. I do tend to pick up and carry rugby ball style quite a lot. Mine is quite small and petite though.

I think you have to keep trying different things until you find THE thing that will work with your son. DS1, 4, is going through the same thing - wouldn't respond to bribery, punishment, naughty step etc. Just recently I have withdrawn all treats and put a star chart on the wall. When he gets 5 stars for good behaviour, he gets to choose a treat. For some reason this seems to be working - no idea why, but I think you just need to hone in to the thing you know makes your son tick. Easier said than done though... it's so exasperating isn't it.

Did you stop at the time and explain why DS1 needed to keep his hat on? Did DS2 have a hat?
Did you ask DS1 if he could have the hat making it clear that if he said no then that was the answer full stop? e.g. you listen to ds2s request and deal with it sensibly, but if the answer is no, it is no.
Does he like being carried? If not can you say "If you continue screaming about the hat I shall have to carry you" If he does can you suggest that you really wanted to give him a piggy back to school, but you can't carry a screaming child.
You kind of need a perpetual artillery of bribes and constraints so you can give a choice. The choice always has to be 2 options you are happy with though and a tantrum is making a choice for the constraint/negative option.
Have you tried setting time challenges? e.g. I wonder if you can get your shoes on in less than 10 seconds? On your marks...

Gosh if the only thing they need to besuccessful in life is to be determine, both of mines are in very good position...

It's nice to hear abut other people though. It helps reminding me thst it's not me but his temperament that makes everything difficult!

I can really sympathise Pitch. Mine crawled round a shopping centre once screaming (age nearly 4) and the LOOKS I got! Only one person came up to me to offer support. I really think peolpe must think we're doing something awful to our children. WE ARE NOT. We just have determined little people. Just think how successful they'll prob be in later life.

Pitchounette I have DS2 who is 4 and still has screaming fits on way to school / when asked to do something he doesn't like etc. He has also never responded to rewards / threats / naughty steps or anything. Not sure this will be very helpful, as I don't think we have found a solution (although being completely consistent and repeating calmly that I will only talk to him when he calms down has helped me deal with it, if not helped stop the behaviour). But the only thing that has recently caused him to stop in his tracks is when I take a toy he is holding at the time and put it in a clear plastic box on top of cupboard / wardrobes / shelves. It seems to distract him just enough from whatever is the problem to focussing on how to get the toy back (BEHAVE YOURSELF ) and it works. Sometimes.

Can I just vent and say he won't bloody wear most of his clothes for no reason whatsoever so the 2 acceptable T shirts are forever in the washing machine. When did 4 year old boys care about this stuff?????? Sorry.

I get you haven't found an easy solution then??

Yes, I think what really gets me atm are the tantrums. I have sort of learnt to deal with the 'No I am not going to do it' and found ways around it but the tantrums ...
Last week, he kicked a fuss because he wanted to have ds1 sunhat. ds1 wanted to keep it to go to school. Shock horror!! ds2 screamed from our entrance up to the school (had to carry him too..), was still screaming in the middle of the playground up to the point that teachers and the head came to see what was happening.... He calmed down only when I pointed out that it was time to go in and that he needed to calm down to ake peace with me (ie have a cuddle together). When he came out 2.5 hours later, he was still moaning about it!!

smee yes I have done that or more exactely, he is normally going in our entrance and is told that he can come out when he is ready to do X. Worked quite well until...he worked out that in some situations, that was actually fantastic.
eg 'I don't want to stay at the table, so I'll kick a fuss, go in the entrance and yeahhh! that's it, I am not at the table anymore !!'

<<whispers>>
The only thing that has ever had an impact on him is a cold shower . I know he really hates that and had to resort to it during our last holidays. It did it once and it worked but it feels totally wrong to do it.

Pitchounette - are our children related? They sound very similar. I have to keep changing the way I (try to) deal with it, as after a few weeks of one method, it stops being effective. I am currently trying "talk and listen" As soon as she kicks off, I ask her if we have a problem and she talks while I listen, and then we swap over. This can stop a huge tantrum and keep her in a state where you can engage with her. I'm sure you know what it's like when they have 'gone' - nothing can get their attention, and mine is often too physical to leave unattended.