http://www.bbc.co.uk/news/uk-england-london-16174789

Also from the ASLEF website

"The union’s members working in London Underground have voted
overwhelmingly to take action on Boxing Day. The dispute concerns the
union’s insistence that the day must be covered by volunteers.

The union balloted its 2,200 Underground drivers and they returned a
92.3% vote in favour of action.

The whole dispute has been about seeking equitable quality time off
for our members but recognising those who do operate the service may
need to be incentivised.

The company is currently offering no additional payments for working
on Boxing Day. The union says its members may need ‘substantial
incentives’ to volunteer.

If the dispute is not resolved, the union intends to take further
action on 16 January and 3 and 13 February."


I wonder how much the threat of strike action is being used as a
negotiating tactic. After all, the dates in January and February are
not public holidays.