There's an answer to the sour cream quandary, Mum!
Apparently, the flavour is right up front, so as soon as the thing touches the taste buds, you get a 'rush', which lasts for a second or so.
After that few seconds, the next one follows with the same result, so the whole tube is made up of 'rushes', and little else!
Not a lot of people know that...;0)