Heathrow Express has introduced a £6.99 single fare for bookings made between three and six months in advance.
The advance fare is some 74 per cent cheaper than the £26.50 cost of buying an Express Saver Single ticket onboard the train itself on the day of travel.
A Business First ticket bought between 30 and 90 days in advance of travel costs £9.99, or £18.00 for a return, compared to £29.50/£53.00 if bought on the train itself.
Heathrow Express said in a statement: "Advance tickets are valid only on the date shown on the ticket and are non-refundable."
Fraser Brown, director of Heathrow Express, said: "Many travellers flying in and out of Heathrow have booked flights well in advance, so it makes sense to book your airport transfer at the same time as your flights for the maximum saving."
Earlier this year, Heathrow Express installed platform gap-fillers at its stations to reduce the risk of passenger accidents.
Source: BuyingBusinessTravel