This is essentially up for discussion rather than a story TL, so here's the OP...
In his 'Riddle of the Sands' Erskine Childers had a theory of the Imperial German Navy building tugs and lighters to make an amphibious landing on the Wash Coast of Lincolnshire, the troops disembarking with naval gunfire support then heading inland to attack the industrial heartland of England. This is averted by our stalwart heroes Davies and Carruthers. Now, suppose Childers had been right and (despite the 'Dreadnought Race') Imperial Germany manages to build the whole scheme and launch the raid early in the Great War (First World War). Could it succeed? The Raid on Scarborough, Hartlepool, West Hartlepool and Whitby showed it was possible for the Kaiserliche Marine to get to the English Coast. The Wash is also far from Cromarty Firth, Rosyth and Chatham, the main East Coast naval bases, so had validity as a landing zone.
Key questions are :-
1. If the raid is launched during Ingenohl's raid on the North East Coast, would it manage to land in the Wash?
2. If launched at a different time, but screened by U-boats, are things any better?
3. Once ashore, what defences would a mix of infantry, cavalry and horse artillery face - and could they reach Sheffield, Nottingham and Doncaster?
4. Could the force return to Germany, or should it be written off like a Commando raid?
5. Could the amphibious raid so dislocate British war-fighting capability that Asquith would sue for peace and break the Entente Cordiale?
Start the attack!