Egon Friedell, "Cultural History of the Modern Age". Note that he actually witnessed these times. He was an extremely well-read man, and he might have known about diplomatic notes. Yes, an Anglo-German alliance might seem ASBish, but the same would have applied to an Anglo-French or Anglo-Russian one.
I would look to Dugdale, German Diplomatic Documents for the period 1895-96. While Salisbury made some tentative suggestions to partition of the Ottoman Empire, which Germany was opposed to, he never made any alliance offers
https://archive.org/details/germandiplomatic02etsd/page/n25
For Salisbury's rejection of any treaty that would commit him to war, see Document 200 Salisbury's memorandum May 29, 1901
This is a proposal for including England within the bounds of the Triple Alliance. I understand its practical effect to be:—
i. If England were attacked by two Powers—say France and Russia— Germany, Austria, and Italy would come to her assistance.
2. Conversely, if either Austria, Germany, or Italy were attacked by France and Russia, or, if Italy were attacked by France and Spain, England must come to the rescue.
Even assuming that the Powers concerned were all despotic, and could promise anything they pleased, with a full confidence that they would be able to perform the promise, I think it is open to much question whether the bargain would be for our advantage. The liability of having to defend the German and Austrian frontiers against Russia is heavier than that of having to defend the British Isles against France. Even, therefore, in its most naked aspect the bargain would be a bad one for this country. Count Hatzfeldt speaks of our "isolation" as constituting a serious danger for us. Have we ever felt that danger practically? If we had succumbed in the revolutionary war, our fall would not have been due to our isolation. We had many allies, but they would not have saved us if the French Emperor had been able to command the Channel. Except during his reign we have never even been in danger; and, therefore, it is impossible for us to judge whether the "isolation" under which we are supposed to suffer, does or does not contain in it any elements of peril. It would hardly be wise to incur novel and most onerous obligations, in order to guard against a danger in whose existence we have no historical reason for believing.
But though the proposed arrangement, even from this point of view, does not seem to me admissible, these are not by any means the weightiest objections that can be urged against it. The fatal circumstance is that neither we nor the Germans are competent to make the suggested promises. The British Government cannot undertake to declare war, for any purpose, unless it is a purpose of which the electors of this country would approve. If the Government promised to declare war for an object which did not commend itself to public opinion, the promise would be repudiated, and the Government would be turned out. I do not see how, in common honesty, we could invite other nations to rely upon our aids in a struggle, which must be formidable and probably supreme, when we have no means whatever of knowing what may be the humour of our people in circumstances which cannot be foreseen. We might, to some extent, divest ourselves of the full responsibility of such a step, by laying our Agreement with the Triple Alliance before Parliament as soon as it is concluded. But there are very grave objections to such a course, and I do not understand it to be recommended by the German Ambassador.
The impropriety of attempting to determine by a secret contract the future conduct of a Representative Assembly upon an issue of peace or war would apply to German policy as much as to English, only that the German Parliament would probably pay more deference to the opinion of their Executive than would be done by the English Parliament. But a promise of defensive alliance with England would excite bitter murmurs in every rank of German society—if we may trust the indications of German sentiment, which we have had an opportunity of witnessing during the last two years.
It would not be safe to stake any important national interest upon the fidelity with which, in case of national exigency if either country could be trusted to fulfil the obligations of the Agreement had been concluded without the assent of its Parliament.
Several times during the last sixteen years Count Hatzfeldt has tried to elicit from me, in conversation, some opinion as to the probable conduct of England, if Germany or Italy were involved in war with France. I have always replied that no English Minister could venture on such a forecast. The course of the English Government in such a crisis must depend on the view taken by public opinion in this country, and public opinion would be largely, if not exclusively, governed by the nature of the casus belli.
Lord Salisbury would never enter a treaty such as the Triple Alliance and he was right to think so. After all, treaties were scraps of paper and Italy and Romania weren't bound by their commitments to the triple alliance