What is the biggest broken promise made by any UK government

 Purely for devilment I asked the AI bot on Google the following question: "What is the biggest broken promise made by any UK government".

I received the following response:

Deciding which broken promise is the "biggest" depends on personal political views, economic impact, and how many people it affected. Several major broken pledges by different UK governments stand out in modern history for their scale and public backlash.

Major Broken Promises in Recent UK History

Student Fees (Liberal Democrats / Coalition Government, 2010): Nick Clegg and the Liberal Democrats signed a pledge to vote against any increase in university tuition fees. After entering government in 2010 with the Conservatives, they trebled the cap to £9,000 a year.

National Insurance (Conservative Government, 2021): Boris Johnson’s government promised in the 2019 manifesto not to raise National Insurance, income tax, or VAT. In 2021, they introduced a new Health and Social Care Levy via a National Insurance rise.

Iraq War Weapons of Mass Destruction (Labour Government, 2003): Tony Blair’s government asserted with "certainty" that Saddam Hussein possessed active weapons of mass destruction. This claim justified joining the US-led invasion of Iraq, but no such weapons were ever found.

AV Referendum and Electoral Reform (Conservative-Liberal Democrat Coalition, 2010): The Liberal Democrats wanted a change to the voting system. The coalition promised a referendum on the Alternative Vote, which was soundly defeated by the public in 2011, leaving the first-past-the-post system in place.

HS2 Northern Leg (Conservative Government, 2023): Successive Conservative prime ministers promised to build the full High Speed 2 rail line connecting London to Manchester and Leeds. In late 2023, the government cancelled the northern leg of the project.

Personally I would add - Boris Johnson; forty new hospitals by the end of 2030 and Keir Starmers; 1.5 million new homes by the next General Election. I know that it is not yet 2030 or the next General Election but the chances of these pledges being met are as good as me being elected the next pope ( I pray that Pope Leo outlives me)