The 'Tallboy' penetrated the U-Boat pens deep enough to render vital equipment useless which is why they threw in the towel over further development. Consequently, those pens were never used.
Sealion would have been a costly invasion for Hitler and impossible without the prerequisite of Luftwaffe supremacy. Even then, it carried a huge amount of risk as did Operation Overlord. Either could have failed. It is my opinion that Hitler's invasion would not have been necessary if Goering had delivered on his assurances and established air supremacy over south-east England. Unopposed daylight attacks on London would have laid waste to the city with industrial, military, cultural and economic targets being selected and destroyed at will and with far greater accuracy than was later to be attempted in the night blitz. Churchill, under pressure from the War Cabinet would have been forced to the bargaining table and a bilateral cease-fire agreed. Hitler only wanted us off his back, not a surrender, which is why he made that 'last appeal to reason' in July 1940. It was RAF Fighter Command which prevented Luftwaffe control of the skies and Churchill's collapse from happening, not the Royal Navy. Churchill may have feared the U-Boats but he would have been sunk without Dowding and Park. Sealion may have been rendered unnecessary by a successful Goering but the invasion was not cancelled because of the threat from the Royal Navy. The brilliant leadership from Stanmore and Uxbridge, Goering's tactical failure to hold London to ransom and Hitler's preoccupation with the Soviet Union can take the credit for that.
The whole concept of Sealion would have eventually amounted to nothing more than a diluted, post cease-fire occupation/monitoring agreement which would prevent any resurgence of British military intentions towards Germany.
'Find your enemy and shoot him down - everything else is unimportant.'
