Ansketil Furneaux is also listed in the Domesday book, and held more land than Odo de Fourneaux. While Odo held land, around Devon and Cornwall, Ansketil held lands to the north and north east of London. He had so much land he had to provide knights for the local minor nobility. 

List of holdings held by Asketil in the Domesday Book:

Village	Shire	Holder in 1066	Fiscal Value
Barham	Cambridgeshire	Eadgifu the fair	2.88
Swannington	Norfolk	Thorbern ‘of Swannington’	0.5
Swannington	Norfolk	Thorbern ‘of Swannington’	0
Harling	Norfolk	Ulfkil ‘of Harling’	4.0
Ainderby Steeple	Yorkshire	Thorkil ‘of East Appleton’	6.0
Ainderby Steeple	Yorkshire	Ulfkil ‘of Crakehall’	3.0

You can view a Map of Holdings here.

According to Keats-Rohan, Alan also owed a ‘fee of the honour of Richmond’ in other words had to provide the service of 8 nights, who rendered castle guard in October to November.  Castle guard was a feudal arrangement where a higher noble placed a kind of a tax, whereby knights were provided in return for the provision of land. The number of knights (knight’s fee) was based on the fief (amount of land held) so fee and fief are intertwined in meaning. 

A wonderful 15th Century Manuscript records the the investiture of Alan as Earl of Richmond by William the Conqueror, and the granting of the Honour of Richmond  (holding Richmond Castle on behalf of the King).