SQL & PL/SQL

this should be easy but I'm struggling
how do you get the text between to points but not including those points in one regexp_substr expression?
for example

WITH t
        AS (SELECT 'blah blah blah start this is the text I want end blah blah blah'
                      txt
              FROM DUAL)
SELECT REGEXP_SUBSTR (txt, '( (start).*end)[^(start)(end)  FROM t

is giving me

 start this is the text I want end

but my tiny brain thought that [^(start)(end)] meant not start or end

so what I am trying to acheive is

this is the text I want