What does that do to the theortical yield on premium bonds?
The odds are, from May, 1:26,000. The 1.3% quoted above (again from May) includes the big prizes (including the £1m prize) so is not, in my eyes, truly representative. I calculate my assumed annual yield as follows:
£25 [smallest prize] x 1/26,000 [odds of winning] x 12 [twelve draws a year] x 100 [to make into a percentage] = 1.15%
This is tax free and better/ comparable to what I can find elsewhere, but with the (small) chance of winning a £1m prize. I would add that as an investment it is far more reliable if you have close to the maximum of £50k invested.