You can remove the Tooltip using the same method and set the text value to null or empty string. Code snippet showing both options below:
toolTip1.SetToolTip(textBox1, toolTip1.SetToolTip(textBox1,
Regards,
Vikram
Thanks Vikram - worked a treat. I was worried that it would show an empty box, in the over-literal way that computers tend to work. Now, let's hope that this gets into the documentation.