Heater valve

I have the S2A type heater tap - the brass one with the little handknob. Its starting to leak and there's no obvious way to get it apart. Its 1/2 BSP and the same as an early Morris Minor. Anyone know how these are made? The knob comes off but how does the spindle come out?

Update. If you take the hand wheel / knob off and put a spanner on the shaft and undo it firmly the splindle, o ring and washer will come out. The splindle is sealed by and o ring between 2 brass washers with the top peened over. Its a bad design and the heat is sure to make the o ring hard and leak after a while.The OEM design has a separate screw in gland so it can be nipped up or changed. Craddocks list the OEM 2 piece type for £20 + £5 P&P when the cheap one piece type is £15 inc post on ebay. Being a natural cynic I phoned Craddocks and asked the person who answered to put up the part (88G588L) on their website, look at the photo, confirm that it has 2 parts with a removable gland nut, confirm that the one of their stock looks like that. Yes to all questions and they even went away for a while to check (or so they said). So I order one for £25 and what turns up? Yep the £15 one peice rubbish one. So I phone Craddocks again expecting something along the lines of "honest mistake, we'll send the right one". But no, what I get is "the small print says it may not look like the picture" and "we haven't had that OEM type for some time.." After I reminded them that they record their calls and I had logged the time and date of the call in which they confirmed the type they stocked looked "exactly" like the picture they agreed a full refund inc postage. But it still leaves open the question as to who in Craddocks you can trust " yes it looks exactly like that sir" or " no we haven't had those for a while..". I got an used OEM 2 part one off ebay in great nick for £13 inc post so its all ended well but I still have to complete an online form to get my refund, and pack and post the wrong item so its a pain that could all have been avoided.

I used to use craddocks as got messed about by paddock some years ago. Went back to paddocks a while ago after being messed about by craddock, probably a cycle here.....