How do you switch the Raleigh RX10 rear light to flashing instead of constant Sorry for the ludicrously specific question, but I just cannot work it out!

Mostly when I turn on my rear Raleigh RX10 USB rechargeable rear light it has a constant beam. Pressing the power button again toggles the intensity of the light. Pressing and holding the power button turns the light off (or back on). Occasionally it comes on flashing instead of constant, but I have no idea how. How can I reliably and predictably turn on flashing mode?
Typical - no sooner posted than worked it out.

Pressing the button turns the light back on, but pressing and holding the button eventually turns it on in the mode it was not in last time (i.e. if it was on constant mode then pressing the button turns it back on in constant mode, but pressing and holding the button eventually turns it on in flashing mode.)