Interesting question Sid.
As a child I learned to cook using tablespoons as measurements but the tablespoons I used were bigger** than the measuring spoons I use now.
I looked it up in an old copy of Mrs Beeton.
According to her US measuring spoons are smaller than UK ones.
3 British tablespoons of flour weigh 1oz; 4 US tablespoons of flour weigh 1oz.
The 'average modern tablespoon' ( according to the editor in 1963 ) was the equivalent of a British standard measuring spoon.
She says a rounded tablespoon has as much above the level of the spoon as below and that the idea of a heaped spoon is rubbish since peoples idea of a heap varies and that if you want half a spoon you should divide along it's length.
I weighed carefully measured flat tablespoons of flour with 2 different measuring spoons, both gave exactly 10g of flour.(metric spoons?)
One of the spoons is scoop shaped and I couldn't manage to make a rounded spoon at all.
The other is spoon shaped and a rounded spoon came out between 18 and 21g so presumably should be 20g.
As the original recipe said a generous tbs of flour I would have put in a rounded (heaped!) tbs 20-25g which is in fact what I use for a similar recipe.
**and indeed they were, according to wiki British tablespoons from the Victorian and Edwardian times (no I'm not that old, but the spoons were) held 25ml or more ;a standard tablespoon in the US and UK is now defined as 15ml
http://en.wikipedia.org/wiki/Tablespoon