The triple lock refers to a safeguard that was introduced in 2010. It’s designed to make sure that the State Pension doesn’t lose value in real terms, and that it increases at least in line with inflation. The safeguard is called a triple lock because it ensures that the State Pension rises by the highest of three separate measures:
Average earnings
Prices, as measured by the Consumer Prices Index (CPI)
2.5 per cent
The way it’s designed means that if, for example, inflation and earnings are very low, the State Pension will rise by 2.5%, but if inflation is higher than earnings or 2.5%, then it will increase by the CPI measure of inflation. The government uses September’s CPI inflation figure to help set the State Pension rate the following April.