Recycling idea to make a raised bed

Had to take car for some work, and we chose a place adjucent to Springfields on the edge of Spalding so that we could have another look at the Festival Gardens there which has various Chelsea style gardens by the major garden design names.  We discovered one plot labelled the "anti design"  and in it was a great idea for a raised bed - instead of expensive railway sleepers, cotswolds stone or rendered walls in the designer plots they had used old black drain pipes. Not sure my photo captures it well but they were varying lengths on 4" black drain pipes enclosing a coffee table size bed and some plants were in the tops of the pipes as well. It worked very well.

Had a look round at home and we have some old down pipes off the demolished sheds but they are washed out grey - wonder if that would work as well and would it be enough?