Who knew that fitting a ruddy Speedo could be such a pain in the bum?
As it is "Wireless" the sensor at the wheel needs to be within 60cm of the head unit. Clearly, the head unit is best placed right in front of you in full view.
The makers clearly expect you to be mounting the sensor on one of your front forks where the spoke-attached magnet can caress it with a magnetic field as the wheel rotates.
No front forks on a Tadpole, so I tried attaching a magnet to the disc-rotor and the sensor to a part of the steering arm. Just did not work reliably.
I tried mounting the sensor and magnet on the rear wheel, but then the head-unit could not connect to the sensor.
I struggled for ages to get the darn thing to work but all to no avail and I was feeling a bit miffed.
Luckily, the thing was only £9.99 so it could be "binned" without too much anguish and I wasn't going to shed tears over it.
However, I had a final try and found a combination that actually worked reliably.
The sensor is now attached to the 12mm x 3mm mudguard stay at the rear of the front offside wheel and the magnet doo-dad passes within the required distance. Bingo!