Vim normal! sending literal <Space> string instead of whitespace character -

i'm not sure i'm doing wrong here.

:normal! i###<space><esc> 

the end result want when execute command on word this:

### word 

but instead this:

###<space>word 

vim's :normal nightmare moderately complicated. don't remember why, easiest way want. need escape opening < in string passed execute.

execute "normal! i###\<space>\<esc>" 

edit: vim doesn't explain why, :help normal

        alternative use |:execute|, uses         expression argument.  allows use of         printable characters represent special characters.