And from their website when purchasing a ticket
PROMO DAY RETURN
TICKET TYPE
SWT▸ PROMOTION
OVERVIEW
Offer consists of Advance Off-Peak Day Return tickets between two stations for travel on South West Trains and Island Line services only. Tickets are priced at GBP15.00 per adult and GBP5.00 per child until 30th April 2016 when booked in advance. This offer excludes travel between 15 February 2016 to 21 February 2016 and 24 March 2016 to 28 March 2016.
CHILDREN
Children are aged 5 to 15 inclusive. Under 5s may travel free of charge with a passenger holding a ticket.
TRAIN OPERATOR
South West Trains and Island Line services only.
BOOKING DEADLINES
This offer is valid to book from 22 January 2016 until 29 April 2016 for travel on Monday to Sunday between 26 January 2016 and 30 April 2016. This is with the exception of 15 February 2016 to 21 February 2016 and 24 March 2016 to 28 March 2016. Customers must purchase their ticket in advance by 2359 the day before travel.
RESTRICTIONS
Ticket restrictions are in place when travelling between Monday to Friday. Travel is not permitted on trains arriving into London Waterloo, Vauxhall, Queenstown Road or Clapham Junction before 1000. Travel is not permitted on trains departing from London Waterloo between 1600 and 1907, Vauxhall between 1600 and 1909, Queenstown Road between 1608 and 1908 and Clapham Junction between 1603 and 1915.
REFUNDS
A full refund less GBP10.00 admin fee can be granted on unused tickets before date of outward travel.
CHANGES TO TRAVEL PLANS
Customers cannot change their date of outward travel once they have purchased their ticket.
DISCOUNTS
There are no further discounts available for Railcard holders and the offer cannot be used in conjunction with any other discount. Some journeys may be affected by engineering work therefore please check before travelling to see if you will be affected. Weekend First Upgrade can be used in conjunction with the promotional tickets subject to availability.
BREAK OF JOURNEY
A break of journey is permitted.
AVAILABILITY
South West Trains reserves the right to withdraw or alter the offer and terms and conditions of the offer at any time.
VALIDITY
Tickets are valid for travel at off-peak times only. Valid on the date printed on the ticket.
Route
Valid only on South West Trains services.