The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

‘Don’t let America,’ added Beaverbrook, ‘think she is settling for these
bases with these old worn-out destroyers.’
Having always suspected that the deal was more about drawing the US
into the war than the need for ships, Kennedy now felt Churchill and
Beaverbrook were revealing their true hands.
In fact most of the ships did require significant work and modification
before they could be used operationally, and although the deal was finally
signed on 3 September, they would not be reaching British ports in a hurry.
But in many ways Kennedy was right; privately, Roosevelt was doing
increasingly more to help Britain. A secret British mission to the US had
also secured sixty new merchant ships to be built by a massively expanding
American Maritime Commission. Mass production of simply built, welded,
440-foot, 11,000-ton merchantmen was underway. Labelled ‘EC-2
Emergency Cargo’ ships, they would later be known as ‘Liberty’ ships.
In return for this clandestine help, Britain agreed to share some of her
technological and scientific advances, including RDF, aerial depth charges,
Huff-Duff, the Rolls-Royce Merlin, and a power-driven gun turret. Another
secret mission, headed by Henry Tizard, set sail for Washington in late
August, carrying with them examples of many of these items. The two
countries also began negotiations to exchange code-breaking information.
Churchill’s long-held plans to bring American muscle to bear were
beginning to take fruit.
Across the Reich, planning for Operation SEALION continued. A
compromise had finally been agreed between the OKH and Kriegsmarine.
There would be no landing at Lyme Bay, but a single crossing of light
forces from Le Havre to Brighton would be carried out in addition to the
main landing between Eastbourne and Folkestone. It was now proposed that
4,500 paratroopers from the 7th Fallschirmjäger Division should be
dropped on to the South Downs in support of the Brighton crossing. Like
most compromises, it pleased no-one. Raeder and Fricke still felt this was
too broad a front, Halder and von Brauchitsch that it was too narrow. Both
OKH and OKW were now agreed that the invasion could now only be
viewed as a coup de grâce – exactly as Hitler had earlier envisaged.
Yet when Raeder suggested that SEALION be converted to an operation
of bluff and nothing more, Hitler rejected the idea out of hand and insisted
genuine preparations should continue, including the build-up of shipping