[0] http://www.worldgovernmentbonds.com/country/united-kingdom/
[1] https://en.wikipedia.org/wiki/National_Lottery_(United_Kingd...
[0] http://www.worldgovernmentbonds.com/country/united-kingdom/
[1] https://en.wikipedia.org/wiki/National_Lottery_(United_Kingd...
It's a little unfair that you said "the Lottery prize fund is weighted very heavily towards the larger sums that you'll realistically never win" but don't qualify that the effective interest rate of Premium Bonds also includes some high value but unlikely prizes. I wonder what the interest rate is for 50th percentile prize winners.
Edit: This page[1] on MoneySavingExpert shows the median (50th percentile) Premium Bond winnings are 1.16% over a year if you have £15,000 invested, and are 0%(!) if you have £1,000 invested. They also have a winnings calculator[1], which shows that median probabilities don't compound over time in the way you'd expect: for £1,000 over 5 years the median return is £50, which is equivalent to 0.98% compound annual interest. (It may actually be fractionally higher because I don't think the calculator assumes you re-invest the winnings in Premium Bonds.)
[1] https://www.moneysavingexpert.com/savings/premium-bonds/
[2] https://www.moneysavingexpert.com/savings/premium-bonds-calc...
[0] https://www.nsandi-adviser.com/july-2018-premium-bonds-prize...
[1] https://www.national-lottery.co.uk/results/lotto/draw-histor...