A bit more info on BA.com
"Hand baggage only - Frequently Asked Questions
How does the hand baggage only fare work?
The hand baggage only fare means our customers bring no hold baggage, but are still able to benefit from our generous hand baggage allowance and take one piece (plus a handbag or laptop bag) on board. The new hand baggage only fares will be available for selected direct European (including domestic) flights to and from London Gatwick and will start at just £39 one way. These fares will not be available on any flights with connections and may not be used via London Heathrow or London City airports.
Customers will be able to purchase the hand baggage only fares via ba.com, which now offers both hand baggage only, and the standard fares for customers with bags to check in.
When does hand baggage only start?
Hand baggage only fares will go on sale on 19 February 2013 for travel from 26 February 2013 on the following routes: Gatwick to and from Amsterdam, Jersey, Dubrovnik, Turin and Tunis.
Other Gatwick shorthaul routes follow at a later stage. The fares apply to shorthaul routes operated by British Airways with a BA flight prefix, and are not available on flights operated by franchise or codeshare partners.
Does this mean British Airways is charging for bags?
No, British Airways will continue to offer shorthaul economy fares including a checked baggage allowance (one item at 23kg). Hand baggage only fares provide an additional lower cost choice for customers who do not wish to take checked baggage."