The German delegation was summoned to Versailles and presented with the terms of the Treaty - massive reparations to be paid, a land-grab, onerous restrictions on Germany's future freedoms, continuing interference by the allies in Germany's affairs. The German delegation was told negotiation of the terms was not possible - it was take it or leave it.
Germany's first democratically elected PM, Philipp Scheidemann, resigned rather than sign such a treaty. In an impassioned speech he said
Which hand, trying to put us in chains like these, would not wither? The treaty is unacceptable.But after Scheidemann, Ebert, as we know, did sign. It later cost him his life. The humiliation of the treaty was so unbearable for Germany it barely lasted fourteen years before conditions allowed Hitler to take power.
It is said that if we fail to learn from the errors of history we are forced to repeat them. As I see Selmayr's smug Moonface smiling superciliously as Britain is forced to accept the Robbins-Selmayr Treaty, a cursed document every bit as humiliating for Britain as Versailles was for Germany, my only surprise is that he is not forcing May to sign it in a railway carriage in the forest of Compiegne.