Our knight is wearing a rivetted steel heaume, or great helm, that is datable to a decade or so each side of 1250. It has a slightly curved top, but doesn't offer the "glancing faces" and increased protection that the slightly later "sugar-loaf" helms offer. The front of the heaume is reinforced with thicker steel strips in the form of a cross. This cross, and its ends, were often decorated or shaped to add interest to the heaume. The whole lot sits solidly on the mail coif, although sometimes it was kept in place by the use of an arming cap, which was a roll of cloth (often part of the padded coif) which accurately and securely located it.
There is some evidence that crests may have been worn on top of heaumes at this point, these would generally have been simple devices denoting the wearer and not the elaborate crests seen in tournaments and later periods.
My heaume weighs about 3kg, and was hand rivetted from curved steel plates - there are no compound curves and complicated beating was not required during its construction. As expected vision is very limited. The presence of ventilation holes in the face guard not only allows some fresh air in, but partly offsets the vision handicap by offering some idea of what is happening directly in front of the wearer.
The body armour is now covered by a surcotte. Heraldry is rarely shown on surcottes of the 1260's, so this knight is wearing Sir John Peyvre's coat-of-arms from the late 1200's.