Britain did attempt to mitigate it, but natural disasters prevented them from doing so effectively as they took out the rail lines to Bengal. Ultimately the famine lasted 1-2 years.

But mate, not even China (and the CCP) denies that Zedong primarily fucked up here (translated from http://www.gov.cn/test/2008-06/23/content_1024934_2.htm):

However, due to insufficient experience in socialist construction and insufficient understanding of the laws of economic development and the basic conditions of China's economy, and more importantly, due to Comrade Mao Zedong and many leading comrades at the central and local levels, who became complacent and eager for quick results in the face of victory, and exaggerated the role of subjective will and effort, they rashly launched the "Great Leap Forward" and the rural people's commune movement without serious investigation, research, or pilot projects. This led to a serious prevalence of Leftist errors, characterized by high targets, blind command, exaggeration, and a "communist style." From the end of 1958 to the early stages of the Lushan meeting of the Political Bureau of the Central Committee in July 1959, Comrade Mao Zedong and the Party Central Committee diligently led the entire Party in correcting the errors that had already been recognized. However, in the later stages of the Lushan Conference, Comrade Mao Zedong mistakenly launched a criticism of Comrade Peng Dehuai and subsequently launched a Party-wide "anti-Rightist" struggle. The resolution of the Eighth Plenary Session of the Eighth Central Committee regarding the so-called "anti-Party clique of Peng Dehuai, Huang Kecheng, Zhang Wentian, and Zhou Xiaozhou" was completely wrong. Politically, this struggle severely damaged democratic life within the Party, from the Central Committee down to the grassroots. Economically, it interrupted the process of correcting Leftist errors, prolonging their existence. Primarily due to the mistakes of the "Great Leap Forward" and the "anti-Rightist" campaign, coupled with natural disasters and the Soviet government's treacherous breach of contract, my country's national economy suffered severe difficulties from 1959 to 1961, causing significant losses to the country and the people.

And you may call 36 million bullshit, but that is the historical consensus. We know from official sources that the population in 1961 is 15 million lower than in 1959, but that difference also assumes no population growth, suggesting a much higher death toll as the Chinese population was growing very quickly at the time. And that's the Chinese estimating it:

• Yu is an independent Chinese historian and a former instructor at the Central Party School of the Chinese Communist Party, estimated that 55 million people died due to the famine. His conclusion was based on two decades of archival research.
• Chen, a former senior Chinese official and a top advisor to former CCP General Secretary Zhao Ziyang, stated that 43 million people died due to the famine.
• Liao, former Vice Director of the History Research Unit of the CCP, reported 40 million "unnatural" deaths due to the famine.
• Yang, Xinhua News Agency senior journalist and author of Tombstone: The Great Chinese Famine, 1958–1962, concluded there were 36 million deaths due to starvation, while another 40 million others failed to be born, so that "China's total population loss during the Great Famine then comes to 76 million." In response, historian Cormac Ó Gráda wrote that the results of a retrospective fertility survey "make the case for a total [death toll] much lower—perhaps ten million lower—than that proposed by Yang".
• Cao Shuji, Distinguished Professor at Shanghai Jiao Tong University, estimated the death toll at 32.5 million.
• Peng Xizhe, Professor of Population and Development at Fudan University, estimated 23 million excess deaths during the famine.
• Li, former Minister of the National Bureau of Statistics of China, estimated 22 million deaths. His estimate was based on the 27 million deaths estimated by Ansley J. Coale, and the 17 million deaths estimated by Jiang Zhenghua (蒋正华).

It's next to impossible to get an exact number because the statistics were being manipulated by local governments at the time to look less bad. There's enough reason to believe Zedong didn't know the full extent of the famine (he seemed to believe it was ~5 million), because he too was fed bullshit from his underlings. So you may call it "Black book of bullshit" but I'm basing myself on sources from China, of people and institutions connected to the CCP.