You realise that they had to weight the war game massively in the Germans flavor to make it fun if even then still a one sided exercise. So despite you inference regarding British posters here the Brits at Sandhurst were actually turning up with one had tied behind their backs to make this more fun, I.e there was artificial weighting going on, but in the opposite direction to the one you imply. The British would be able to see the barges embarking in their ports (this leaves aside the point the British would have seen the barges mass even before embarkation*), the invasion fleet would have to form up and would been moving very slowly and there would be no issue tracking them. Now what if there was weather bad enough to obscure them form British coast watch (and naval and air patrols), than OK, but to be honest any weather bad enough to obscure the invasion fleet from discovery is also weather bad enough to mean the invasion fleet itself would get lost or even just be lost. It actually irrelevant because even if the the first wave of landing 'craft' reach British shores it's hardly game over with a Swastika planted on Buckingham palace. *This actually happened at one point, they started to consolidate some barges for a test exercise, guess what the RAF flew a mission and bombed them We know no such thing. That was general policy mainly due to the risk that if you sent Battleships where the German battleships weren't you risked the German slipping their battleships out into the Atlantic (as you say below). In the case of invasion though, yeah the RN is going to deploy because stopping a marine invasion of the home island has been the RN's number one and overriding priority since it was formed. There was plenty of RN home fleet about. Even if you don't know exactly which beech the German intend to land at, there's actually only so many options due to geography and the speed of the craft. It was going to take 2 days for the barges to get to the closet possible beeches, to expand the possible landing sites would mean extending that time considerably. On top of this remember you talking barges going 3knts vs. destroyers going at 20-25knts. The battleships are a red herring anyway, they won't be needed. I doubt it (sea state 2 is nearer the mark), but more importantly I doubt it even more when they are in daisy chains of barges, river boats & pontoons being largely run by press-ganged lowland and civilian river pilots trying to maintain a mass formation by communicating by load hailer, who don't know the waters, crossing the channel under attack (or in weather so bad as to hide them from attack) It's the same information, the fleet was never just going to river barges and pontoons. Of course the Germans had access to more sea worthy boats, it's just they didn't have enough so they had dilute the invasion fleet with all sorts of less sea worthy boats and actual rafts. Even then the more seaworthy boats weren't landing craft, but just better boats. So they would still have to either capture a port to off load at or rely on very slow ferrying of the troops as they moored of shore. Ironically the river barges and pontoons could in theory* land on beeches and off load, on the term is actually "run aground" so once they're do that there's no guarantee they'll be able to move off again. (plus of course they have to get to the beech first). This last is important because you have to remember the Sealion plan involved not just the barges and pontoons getting across and landing, but moving off the beech, travelling back to their embarkation points, reloading and repeating the exercise! *They did a test run, unladen in broad daylight in calm weather. They towed a bunch of then a few miles off a beach and set them to land, in those perfect conditions (clear sky, unladen, no enemy, not after two days rolling on the channel chucking their guts up, not with press ganged pilots, knowing the exact beech to land on) .....50% success rate of getting ashore OK a few problems with this in general and specifically in comparison to the battle of France 1). this after the battle of Britain so the LW is not in the same state as it was in the Battle of France 2). In the battle of France the RAF was a lot smaller in total than n Sep40 and was only smaller subsection of that as well as operating on foreign territory while ground forces were retreating back towards them 3). In the BoF the LW only had one job to do, in Sealion it frequently gets given lots of jobs to do namely, defend the flotilla, defeat the RAF in the channel, defeat the RN in the channel, contest SE England airspace distract Britain in London help take those airstrips in SE England and so on. (remember it has already recently failed to do only a few of these things a few months earlier) This the LW that that just lost the BoB yeah? What are the RAF (who they just lost to) doing at this point? More importantly say they sink a destroyer or two or fuck it lets say five, no ten, how about fifteen and two light cruisers ....so what? You think Britain's going to say "hmm we're losing ships, ahh fuck it let's let them invade and give up out greatest advantages".