Topped Leylandii by mistake

When I planted some five foot Leylandii last year I took off about six inches off the top ie the growing tip because I thought it might help establish them better.Now twelve months on they are growing outwards but are flat topped with no or no discernible vertical growth.Will they grow vertically or have I made a big mistake as I wanted them to grow quickly and keep them at about eight feet.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.