13 Property, plant and equipment
 
 
  Leasehold 
improvements, 
land and 
buildings 
£m 
Plant and 
machinery 
£m 
Total 
£m 
Cost      
At 1 January 2005 27.7  184.4  212.1 
Subsidiaries acquired 1.8  2.1  3.9 
Additions 7.7  42.0  49.7 
Disposals (0.8) (1.5) (2.3)
At 31 December 2005 36.4  227.0  263.4 
Subsidiaries acquired 1.4  0.9  2.3 
Additions 7.4  55.6  63.0 
Disposals (5.0) (55.0) (60.0)
At 31 December 2006 40.2  228.5  268.7 
Depreciation and impairment      
At 1 January 2005 10.4  72.6  83.0 
Provided during the year 3.5  28.2  31.7 
Disposals (0.3) (1.1) (1.4)
At 31 December 2005 13.6  99.7  113.3 
Provided during the year 4.7  37.5  42.2 
Disposals (3.3) (54.5) (57.8)
At 31 December 2006 15.0  82.7  97.7 
Net book value      
At 1 January 2005 17.3  111.8  129.1 
At 31 December 2005 22.8  127.3  150.1 
At 31 December 2006 25.2  145.8  171.0 

The net book value of plant and machinery includes an amount of £0.1m (2005: £0.2m) in respect of assets held under finance leases. The net book value of assets held by the group for which it acts as lessor, amount to £4.7m (2005: £8.7m).