Pastimes:Perplexity

What is the next letter in this series:

T S E T R N S ... ?

and this one:

S T N D R D T ... ?

and finally, try this one:

E E I L P P R T ... ?

(they have no connection with each other whatsoever).

A Larousse Desk Reference Encyclopedia will be awarded to the first correct answer opened on 28 August. Answers to: Saturday Pastimes, the Independent, 1 Canada Square, Canary Wharf, London E14 5DL.

3 August answers:

Steven Redgrave (starved revenge); Coxless pairs (closes praxis), Gold medals (small dodge) Winner: DG Browning (Leicester).