Chairs
Backed chairs were not common and should be restricted to one per Herred (at most). They should be based upon a suitable period find, such as the Oseberg chair, and should not be large or ostentatious.
Thrones
Any ornate and/or large backed chair will be considered to be a throne and as such would only be allowed for suitably costumed and equipped characters, and only allowed in the LHE with specific approval of the LHE co-ordinator and/or the authenticity team. To ensure that an “ordinary” encampment does not look richer than any royal encampment, thrones will not be allowed at an event where there is a scripted Royal presence in the LHE. The Society reserve the right to commandeer any throne for the use of the King.
Oseberg ship burial
The only archaeological find of a truly Viking "chair" (ie a seat with a back, as opposed to a bench or stool without a back) is the one found in the Oseberg ship burial (interred c.834).
The Oseberg chair is fairly small and the back is relatively low compared with a modern chair. It has an open space where the seat should be, and holes around the perimeters suggest that it had a web of string or similar to form the seat itself. Reconstructed examples suggest that the webbing probably supported a cushion, because otherwise you sink into the webbing and the perimeter woodwork digs into the backs of your thighs. Despite this rather obvious design requirement many reconstructions go without the cushion and as a result the chairs are fairly uncomfortable. Accounting for the height of a cushion, the actual height of the chair back would support only the lower lumber region of a person's back.
The Oseberg chair is the only truly "Viking" period backed chair ever found, and this was in the burial goods of a queen. This suggests that chairs as such were rare, although considering that very little other furniture has survived this is probably a good case for the lack of evidence is not evidence of a lack of existence. The sagas suggest that every decent longhouse had a high chair for its jarl owner, and there are numerous mentions of benches, yet archaeological evidence for these benches is as noted above sparse.
One specific other source of evidence for backed chairs is the Lewis chess sets, where the kings, queens, and some of the bishops are all seated on chairs. This does however reinforce the idea that chairs were restricted to the rich and powerful, and it has to be considered that the chess sets are fairly late in our timeframe. It is however interesting that all of the chairs within the chess sets are very similar in style and design to the Oseberg chair, with a relatively low back. This stylisation of a 'throne' suggests that the design of backed chairs followed the Oseberg pattern throughout our period.
Despite the evidence we do have, the rarity of backed chairs is notable. They were definitely not in everyday use, and probably reserved for those in high office, or at least the very high status.
Chairs from Anglo-Saxon England
While no chairs survive from Anglo-Saxon England, chairs with a similar box construction are also illustrated in Anglo-Saxon manuscripts, for example king David on the Harley Psalter 603 f1.v (Shown in Anglo-Saxon textual illustration, Ohlgren 1992, plate 2.2).
There are a number of examples of chairs and benches recorded as "Viking" from Scandinavia (especially Sweden). These date from later, into the twelfth century.
These include an eleventh century chair back found in Lund. This is illustrated in "From Viking to Crusader" (Edited by Roesdahl & Wilson,1992).
"Bede's chair"
“Bede's chair” is attributed to the Venerable Bede who died in 734, though it is actually much later in date. Some local stories say that the chair belonged to prior Aldwin who re-founded the monastery in around 1072 after the Norman conquest, as happened at many Saxon religious sites (including Lindisfarne), but even this date would put the chair into the very late eleventh century.
The chair has been carbon dated to being not earlier than around c 1300. It is likely to be a chair that belonged to an abbot of the re-founded Norman monastery, or considering the plain design it might even be a surviving section of some larger choir seating. The design of the Bede Chair is typically episcopal in that its seat isn't very wide, so you perch on the edge rather than sit in the chair. The idea being that even a high up cleric wasn't allowed to get too comfortable. In this the wooden chair is similar to stone misericords built into the walls around later chapter houses.
Credits: with thanks to Steve Lines.