The 'triple lock' is a government commitment in the United Kingdom that dictates how much the state pension rises each year. Under this policy, the pension payment is adjusted based on the highest of three specific figures: the rate of inflation (measured by the Consumer Prices Index), the growth in average earnings, or a fixed floor of 2.5%.

The policy was introduced to ensure that pensioners do not see their standard of living decline relative to the rest of the working population. By selecting the highest of the three metrics, the government guarantees that the pension keeps pace with the cost of living and wage growth, while the 2.5% floor provides a minimum guaranteed increase even during periods of low inflation or stagnant wages.

While the policy is popular among retirees, it has been the subject of ongoing political and economic debate. Critics often point to the long-term fiscal sustainability of the commitment, noting that it can lead to significant increases in government spending during years where wage growth or inflation spikes. Proponents argue that it is a vital social contract that prevents pensioner poverty and provides financial security for an aging population. The mechanism remains a central feature of UK fiscal policy, though it is frequently reviewed during budget cycles as governments weigh the cost of the commitment against other public spending priorities.