Since this set is a first printing, the front cover doesn't have blocked-out text at bottom left, & the name "Skyler" hasn't been corrected in an addendum to "Apollo".
As mentioned previously by Shaquille, Don Lawrence was one of the artists whose work was 'borrowed'. The Hamlyn hardback Trigan Empire book was published in 1978, so it seemed reasonable to assume that may have been one of the sources. And indeed, on p.170:
Picture Credit: The SPLAT Scan Archives
© Tom Vinelott 2023