J B Dance! In Radio Constructor, I have not heard of him or that for years! My main technical reading, loved "Smithy". They even published an article of mine!
The valve will almost certainly be fine in another position in the amplifier so keep it as a spare.
The input to the first stage of guitar valve amps is almost always DC coupled, i.e. no capacitor. Cannot think why? Such a capacitor could be a very low value ~1nF and the signal from guitar so small, little chance of 'blocking'.