I lack the space and the tools to do it, but my method would yield something like this;

Take a steel tape measure or similar semi-rigid material, of length 6.371 metres. This corresponds to the mean radius of Earth of 6,371km, according to the textbooks.

Fix it at one end, such that you can rotate it around this end, and with a pen or pencil attached to the other, draw an arc on paper. This is a scaled-down Earth surface arc, such that 6,371km is scaled down to 6.371 metres. 1km = 1mm at this scale.

Measure out 7.24cm of this arc. This is equivalent to the 45 miles or so from the observer to the Reunion Tower.

72.4km = 72.4mm at scale = 7.24 cm

Draw the heights of observer and Reunion Tower at each end of this measured arc, and the intermediate hill at the appropriate distance from each, between them, and join them with a sightline (the blue line in my example).

Herein lies a problem at this scale, for each height (Ho = 259m, Hi = 198m, and Hr = 302m), is less than 1km, and hence at this scale will be less than 1mm. Not practical to draw them by hand.

So whilst I have the method, I lack the space and equipment to achieve this by hand. Would need a 63.71 metre tape measure to draw the arc

You can see how it works, though...

Perhaps JSS could use the digital drawing tool he used above to do this...?