Securing decking posts

[alexakasloth]

How would you go about securing down some upright posts for decking?

There's a bed of hardcore there from the existing patio and don't fancy digging it out. Could I secure some post supports into concrete blocks and bed these down?

[edit]
Alternatively I could build it slightly bigger over the grass and concrete in several posts.

 

[alexakasloth]

Thanks for the replies guys. I'll go with a row of posts concreted in to stop sideways movement, the others I can rest onto some slabs.

It's ~4m wide x 3m deep all ground level. I think I will do the first 4 going across concreted in, it's just to stop any potential sideways movement.