Erskine's reasons for dismissal of the value of the capture of U 110:
Quote from his afterword; " While BP received an Enigma machine and rotors from U 110, they did not help, since BP already held several machines and all eight Enigma rotors. No Hydra Allgemein Enigma keys were taken from U 110, although an Offizier keylist for April was seized. The 'Einstellung and Buchstaben" (settings and letters) recovered from U 110 for April and June were not Enigma keys, but merely recognition signals for use with flares and signal lamps."
Dave Saxton wrote:Retaining contact long enough to bring the Home Fleet battle groups in is the main problem for the British as I see it. Catching a glimpse of the enemy is one thing, but shadowing for hours on end is quite another. Unless there are prolonged periods of unlimited visibility- rather unlikely-it seems a difficult task without capable surface search radar. For example, when the Scharnhorst and Gneisenau tried the Gap previously they were spotted by a British cruiser briefly. The cruiser was unable to retain contact. It reported that it had seen the Hipper. The Germans will know by local radio intercepts if they were being shadowed or not as they did historically.
When the Scheer came back through the Denmark Strait in March of 41 its radar warned it of an approaching patrol in time to duct into a near by fog. This was a daylight encounter. They watched the British cruiser steam by. The British look outs never saw the Scheer. A second encounter came at night. In this case the Scheer's radar was not operating because the moisture resistant cases had been carelessly not closed up. The Scheer suddenly found it self in the wake of an enemy cruiser no more than 3,000 meters away on a bright star lit night. But once again the British look outs never saw the Scheer. This was in the Denmark Strait so the Germans really had no where to go. Such were the difficulties faced by the British patrols in any of the northern passages.
As Mr Raven points out, Enigma Intel will be available after the 29th due to the capture of Enigma keys from U-110 and the weather ships. The British could use Ultra Intel to help find Luetjens once out in the Atlantic by the arrangement of meeting of supply ships. The keys were not those used by surface warships in distant waters, but Prinz Eugen will need frequent re-fueling. The British will need to be careful in the use of this Intel so that the Germans don't become wise to it and change the keys.