clout nails. hammer them through a few mm form the edge of capping into cement. if the cement is too hard, a red plug next to capping with nail half in and hammered over does the job
for capping you can buy proper capping nails which have a small washer which slides up shaft as you knock them in - as for oval tube i drill a 5.5mm hole at various points either side of tube and then use galvinised conduit crampets which i bend the tops over and they work extremeley well.
All depends what wall is made of. Breeze and thermalite you can usually get away with 65mm galv nails. If its old walls you usually end up having to use extra long nails in sand and lime. For flettons if mortar is not to hard I use nails out of clips in morter but as always every job is different and will come with experience.