Problem with Close up 1D MkIII + 100mm2.8 + 580EX

I have tried this combo for the first time indoors and taking shots at minimum focus distance 1:1 I cant get the subject illuminated with the 580 pointed down? Should this be possible or is the flash firing over the top of the subject due to hot shoe height?

It's possible the end of the lens is shading the subject from the flash when mounted on the camera. many of us use flashbrackets to get round this( see this thread https://photography-on-the.net/forum/showthre​ad.php?t=142566 ). You may be able to solve this by getting a polystyrene disc (as often used on frozen pizzas), cutting about a 6 inch circle and the cutting an offcenter hole to just fit over the end of the lens with most of the disc above the lens, so the flash fires through it. This acts as a diffuser and sort of secondary light source.
Brian v.

Thank you very much Brian, I'll give that a try. Funnily enough I bought a frozen Pizza this week for the first time in years - just retrieved the disc from the bin!

Here's a couple images of my home made macro lighting set-up. Maybe this will help you. You'll need to get a Off Camera hot shoe cord or some sort of wireless system to trigger the flash.

Thanks Chas, nice Bee shot.