3-dimensional, vector geometry, lines, distance, perpendicular.
[STEP II 2002 Question 7 (Pure)]
Intersection of surface with spheres, Little Fitton.
[STEP I 1993 Question 8 (Pure)]
Area of surface, sphere, conic section, tangent, circle.
[STEP III 1989 Question 1 (Pure)]
Underground Mathematics: Selected worked STEP questions
STEP Question database
University of Cambridge Mathematics Faculty: What do we look for?
University of Cambridge Mathematics Faculty: Information about STEP
University of Cambridge Admissions Office: Undergraduate course information for Mathematics
Stephen Siklos' "Advanced Problems in Mathematics" book (external link)
MEI: Worked solutions to STEP questions (external link)
OCR: Exam board information about STEP (external link)
AMSP (Advanced Maths Support programme): Support for University Admission Tests (external link)