Longer reach router bits - specifically, in the UK

I’m trying to find long reach bits, to do useful work over the edge of a 4 centimetre cliff, in wood, namely pine and plywood. Currently, the collet of the router will catch the workpiece when making cuts this deep. My present bit of choice is an end mill, but almost anything small would do really. The router takes 1/4" bits, which I think is part of the problem.

RDG Tools have some ‘long series’ bits, but they only seem to actually extend the cutting surface of the bit, not the shaft / total length. Maybe I’m looking in the wrong place? I’m aware that the longer the shaft, the more strain on the bit, but this would only be used for detail work.

Thanks in advance for any advice offered.

I haven’t seen one that long. I would imagine you might need a much slower rpm as well.

Maybe make the part in two layers?

I was trying to avoid that, but yes, I suspect that’s what I’ll end up having to do…

Either that or get someone to make a long bit specifically for pocket detailing work.

The only ones I can find on eBay are 4 flute, which won’t work for crap with our routers.