Some progress with Bertie's behaviour around my boys! I haven't had the chance to get him fitted for a muzzle yet, my local pet store hasn't got the right size and I have to wait until they have new stock in.
So, last Sunday I was having a family dinner with all 3 boys 'round and my D-in-law. I made them keep all interactions with both dogs to a minimum, as I've noticed Bertie's behaviour is worse when they over-fuss Rosie. Bertie had to sit and give his paw to get a treat, then get sent away until invited back to sit again. Then we sat at the dinner table with neither dog allowed near. They settled down and it suddenly occurred that I'd elevated the boys' status by us eating together while the dogs were hungry! It worked a treat, with Bertie only 'freezing' once, gently reprimnded and sent away by my midle son, who then recalled him to a sit and praised him.
So last night an unexpected visit from the boys in the evening, followed the same 'no fuss' policy, and again, Bertie was working to get small amounts of low-key attention. For the first time ever he worked as hard as he could for my youngest son to let him very briefly lay on his back in his lap, with his ears pinned to his head and leg lifted in total submissive position!
Finally the boys have got the message that BOTH dogs are better behaved if they are at the bottom of the pack and that letting Rosie jump all over them is one of the triggers for Bertie getting wound up, as he tries to assert his dominance if there is excitement. Seeing Bertie working so hard to be good, again every one of his 'sits' at their feet was with submissive leg lift, the boys fell into more calmly assertive roles and relaxed with him instead of being tense expecting him to snap or growl.
Still a work in progress, and yes I'll still get the muzzle as soon as his size is in stock, but a step forwards at last!