Although officially neutral, Britain had supported the Confederate states in the American Civil WarThe context of the statement is the cancellation in 1866 of a trade treaty between Britain and the United States signed in 1854 governing trade between British North America and the USA.
I wonder what Abraham Lincoln might have had to say about the efforts of Britons to oppose the Confederacy?
Mr Lincoln, in a letter dated 19 January 1863...replied with the words that are inscribed on his statue: 'I cannot but regard your decisive utterances on the question as an instance of sublime Christian heroism which has not been surpassed in any age or in any country. 'It is indeed an energetic and re-inspiring assurance of the inherent truth and of the ultimate and universal triumph of justice, humanity and freedom...Whatever misfortune may befall your country or my own, the peace and friendship which now exists between the two nations will be, as it shall be my desire to make them, perpetual.'Lincoln in this passage refers to the workers in Lancashire cotton mills support for the war against slavery, despite the fact that they were undergoing terrible hardship because there was no work. The mills' cotton normally came from the states that had seceded, those states (and the Union blockade) had restricted the export of the cotton, so the mill workers had no work. You can read more about the affair in this BBC.com News post. You can also listen to an In Our Time episode about the Lancashire cotton famine. The Union was without doubt the favoured side of the British people in the war, although opinion among those whose job it is to worry about Britain's national security saw some advantage in a United States divided into two.
What thecanadianencylopedia.ca must refer to are the Alabama Claims. The basis for these claims were the raids of five ships that were built in British yards but sold to the Confederate States' Navy. These raids sank over 150 'Northern ships' in the course of their commerce raiding during the War Between the States. Given that Britain remained officially neutral throughout the war, the question of whether ships built by private British interests for foreign buyers that put to sea in an unarmed state raised technical legal questions far removed from the blatant Union abuse of British neutrality in the Trent affair. That the British government did not want to get mixed-up in a private transaction cpncerning the Alabama following such a presumption on the part of the American navy can at worst be regarded as a bit of tit-for-tat diplomacy. In the end, the British prime minister and foreign secretary both accepted that they should have stopped the Alabama putting to sea, in the same way that the President Lincoln disavowed the actions of the US naval officer in the Trent affair.
In fact, the Alabama claims led to an attempt by the United States to dismember Canada, suggesting that British Columbia, parts of western Canada between the Rockies and Manitoba and a portion of Nova Scotia might be appropriate return for the losses to the US merchant fleet. Of course, one won't find American territorial ambitions in Canada mentioned. Having lived there for several years there are moments when to my mind there seems to be an ideological war in Canada against Britain, which I neither understand the necessity for, nor believe all of its practitioners fully understand the potential consequences of it.
Of course, having worked in publishing for many decades I know what happened here. There was a word limit and a more nuanced description of the fraught state of Anglo-American relationships during 1861-72 was compressed to the point that it became wrong. Still, one would expect it to have been corrected in the last listed revision of the original article, last July.