Speaking personally I would not rate Slim as the best British General of the War. If O'Connor had not been so unfortunately captured in the Western Desert then I think there would of been a commander to brag about. He really genuiniely understood armoured warfare in a way few commanders on either side did. Auckenlech is another contendor. Took the battered and broken eight army and turned it around to repulse Rommel at El Alamian. Or Montgomery, the man with the plan, He certainly won a lot of battles in his time and although he was critised for being slow he also made sure he never got beaten. As for Slim if you want to talk about achievement how about the fighting in the Arakan where Slim showed some real ability. He together with Lomax deduced the Japanese planand for the first time in Bruma campaign Britain didn't get beaten. A good commander I'd say, but not the greatest.