Short answers, pulled from the story.
The Lighthill report is a 1973 scholarly article by James Lighthill titled Artificial Intelligence: A General Survey, commissioned by the British Science Research Council. It evaluated AI research and concluded that no area of the field had produced the major impact that had been promised, forming the basis for the British government's decision to end support for AI research in most British universities.
James Lighthill wrote the report. It was commissioned in 1972 by the Science Research Council, which asked Lighthill to make a personal review of the subject of artificial intelligence. He completed the report by July of that year.
The report organized AI research into three categories: Advanced Automation, Computer-based Central Nervous System research, and Bridge or Building Robots. It found that AI techniques failed to scale beyond restricted domains due to the combinatorial explosion, judged robot-building projects entirely disappointing, and predicted that the bridge category would be abandoned within roughly 25 years.
The combinatorial explosion refers to the way the number of possible states in a problem grows unmanageably large as the problem's scope expands. The Lighthill report identified this as the central flaw in AI research, arguing that techniques that worked in small domains could not scale to real-world problems because the knowledge required quickly grew too large to manage by hand.
On the 9th of May 1973, James Lighthill debated his report's findings at the Royal Institution in London. His opponents were Donald Michie, John McCarthy, and Richard Gregory, three leading AI researchers who challenged his conclusions in person.
The report's pessimistic assessment of AI research formed the basis for the British government's decision to end support for AI research in most British universities. This withdrawal of funding drained institutional momentum from the field and contributed to what is recognized as an AI winter in the United Kingdom.