This is the attempted seduction scene that was edited out for American release. Willow (Britt Ekland) was the representative of the goddess of love/sex and as such was charged to test the "purity" of Sgt Howie (Edward Woodward). Her song and dance is erotic and odd. A true classic, I believe. Ekland was pregnant at the time and as such a body double was used for the full (behind) shots but agreed to do the topless shots herself.
Yes, the Sneaker Pimps covered this song.