From Checkpoint Charlie: The Cold War, The Berlin Wall, and the Most Dangerous Place On Earth by Iain MacGregor (Scribner, 2019), Kindle (pp. 235-237:
When First Secretary Mikhail Gorbachev arrived on October 7  to participate in the East German regime’s fortieth anniversary celebrations, Susie Corbett was in East Berlin on a regular shopping trip. “As far as I could see from touring the center of town in my car,” she recalled, “it seemed the whole place was enjoying a fête, with red Soviet flags dressing up the main thoroughfares and government buildings and the population seemingly keen to celebrate, too. Nothing seemed any different to my previous visits.” After a massive military parade, the Soviet leader’s pronouncements to the media in a public walkabout (unheard of by any Eastern Bloc leader until then) shocked Honecker and those closest to him in the SED hierarchy—Gorbachev announcing to the cameras, “A party that lags behind the times will harvest bitter fruit.” This was a clear and honest appraisal of the pressure the country was under from internal protests and his knowledge of the perilous financial state of the GDR. The planned torch-lit parade that evening, which would praise the creation of the GDR, the rule of the SED, and of course the leadership of Erich Honecker, turned into a farcical spectacle. Gorbachev looked on incredulously, standing alongside the grimacing East German leader, as they watched supposed loyal party activists shout to the Soviet general secretary, “Gorbi, Gorbi—help us!”
For the ailing Honecker, this was a disaster, which had quickly followed a fiery meeting, with the German and Russian men clashing verbally in private and in a meeting of the East German politburo, Honecker deriding Gorbachev’s reformist policies compared to what he believed were the GDR’s economic success. The Soviet leader had audibly hissed his derision at the old East German, with Honecker’s excuses met by deafening silence around the politburo table.
Robert Corbett received a request from Britain’s ambassador to West Germany, Sir Christopher Mallaby, to discuss the situation. Televised coverage of an October 16 march in Leipzig had been aired on West German TV following secret video recordings that were smuggled out of the GDR. Now the world could see hundreds of thousands of East Germans demonstrating, instead of just the hundreds who were trickling into the West German embassy compound in Prague seeking asylum. It was a far bigger story.
A general atmosphere of unease gripped Berlin, reinforced when the sudden news came through that Erich Honecker had been forced to step down. The younger generation within the East German politburo, led by his deputy Egon Krenz, had taken Gorbachev’s visit and his official rebuke on the need for the regime to change as a signal to make a grab for power. Krenz had long been seen as the heir apparent and had risen through the SED ranks to become secretary of the central committee. Crucially, he oversaw security for the country and was able to persuade the head of the Ministry of State Security, Erich Mielke, to support his bid to oust the ailing leader. The week after this bloodless coup, more than 350,000 people took to the streets of Leipzig for a second mass rally. Secret dossiers had been prepared for the new leader that outlined what kind of state he was now inheriting from the man he had unceremoniously ousted. The GDR was in effect bankrupt and surviving on enormous loans from the Federal Republic just to keep going in the short term. Debt was piling on top of debt to the international markets. Was the game up? Ambassador Mallaby and his fellow ambassadors of the USA and France were deeply concerned and this was reflected in the by now constant updating of plans by the three Western Allied Commandants and their staffs.