Trouble with dust

When I started processing the day's photos I discovered they all had a large mark on them near the top left corner - especially noticeable on this one, which had a a light-coloured wall in the background and taken with a fairly small aperture: dust on the sensor. The dust was not visible with the naked eye, and repeated use of a blower had no effect. SO it was time to inspect it more carefully, and eventually resort to sensor cleaning swabs. I think that I have fixed it, but tomorrow's photos will be a proper test.