People from southern England - and London in particular - are often unable to pronounce the ‘th’ at the beginning of words like ‘thought’ and they omit the ‘ts’ in words like ‘letter’. It isn’t laziness, or lack of education, or slang - it’s the result of their own particular regional accent.
Evian //I remember seeing a clip recently about some children in Essex who said the right words but didn't know how to pronounce them properly and therefore spelt them totally incorrectly.//
That doesn’t work at all. I say ‘glarse’ and ‘parse’ instead of ‘glass’ and ‘pass’ – and oddly enough, so does the Queen.