Speaking on today's This Morning, the 53-year-old claimed that his deathbed scene with Pat Butcher provoked a huge reaction among fans.
"She helped establish Derek more than anything else," he told ITV1's magazine show.
"Just the reaction that she showed to him and the relationship they had was just phenomenal and I bless her for that."
Evil Derek mocked a dying Pat in an emotional New Year's Day edition of the Albert Square soap, which marked St Clement's last appearance as the Walford matriarch, having played her since 1986.
> EastEnders Jamie Foreman: 'Derek will surprise viewers'
Watch Derek and Pat's defining EastEnders scene below: