Constructing a 10' wall/fence

I would like to replace a screen of 12' high conifers with a 6' high wood panel fence sitting on a 4' wall. (ie 10' in total height). Ideally would like 4' of 'faced' gravel boards with wooden fence panels above. Can't find any concrete fence posts taller than 10', which will reduce in height when cemented into ground, therefore can't get my 10', which is essential. Can one get taller ones ? Any better ideas out there...............?

no youll struggle to get them that height. they will be very prone to wind damage at that height, and also it will need planning permission to go to that height