RE: Banking sector fragility. An interesting watch25 May 2026 09:49
None of what you have written negates the mathematical reality regarding savings as a distinct asset class. If interest rates are high and inflation is low, cash serves as a reasonable wealth-preserving asset, but if interest rates are low and inflation is high, it becomes a depreciating financial asset in real terms. Your specific example regarding a £500,000 balance actually highlights this issue: if you are earning 4.5% interest while headline inflation sits at a higher rate, the real purchasing power of that total £500,000 principal is actively shrinking year-on-year, regardless of whether the nominal interest payout covers your immediate monthly bills. Relying on nominal returns to meet cash flow requirements does not alter the fact that the underlying capital value is being eroded by inflation. Currently, interest rates are working in favour, being higher than the headline inflation rate, but as was seen in 2023, inflation peaked well above available savings rates, which significantly eroded the real value of cash capital.
To look at your £500,000 example through actual ONS data, consider the peak inflation period of 2023 when headline CPI hit a high of 10.1% while the average building society or bank ISA rate sat around 4%. Over that single year, your £500,000 principal generated £20,000 in nominal interest, moving the account balance to £520,000. However, because goods and services that cost £500,000 at the start of the year inflated to cost £550,500 by the end, your cash fell £30,500 short of keeping pace with the cost of living. In real terms, the purchasing power of your half-million pounds actively shrank to just £472,300. This year, the asset class has recovered somewhat because the economic dynamic has flipped; with the Bank of England base rate having held high and inflation dropping down to 2.8%, a 4.5% tax-free ISA yield finally delivers a genuine, positive real return of around 1.7% above inflation, allowing the core purchasing power of that principal to slowly repair.
Building a cash ISA balance to that £500,000 mark is technically possible through historical limits and compounding over 22 years, it would have required an exceptional level of financial discipline. A saver would have needed to track changing government limits every single April since 1999, deposit the maximum allowed on day one, and actively transfer the entire accumulated pot regularly to highest-yielding providers to prevent the capital from stagnating at near-zero rates during the 2010s. I like your example but for the average saver would be implausible to produce.
I only have around £30k in my cash ISA