Just type in 'FALLFASHION' at the checkout from what I can see it applies to all customers not just new customers,I know there is a £10 off £50.00 spend but if you have used that this may help
Terms & Conditions of this Promotional Offer
Your entry to this promotion is subject to these terms and conditions.
£50 minimum purchase required.
This offer cannot be used in conjunction with any other promotional offer or discount.
Offer valid until midnight on 9 October 2007,
This offer is not available on purchases from the John Lewis Gift List and cannot be used to purchase gift vouchers.
This offer is not redeemable in John Lewis department stores, Waitrose supermarkets, Waitrose Deliver or Ocado.
£5 Coupon valid for credit/debit card purchases only (no bankers draft or personal cheques can be accepted with voucher).
John Lewis normal returns procedures apply.
All other John Lewis terms and conditions apply