We were on port tack close reach to leeward, inside and overlapped on a boat slightly ahead of us, approaching a mark that needed to be rounded to starboard.

Immediately after the mark and perhaps 3 boat lengths away is a shoreline that necessitates holding a higher reach before being able to fall away to the next mark.

Hailed for room, the other boat gave us about a boat length's room on the buoy, and we got around fine, gybing as was required.

Had to keep the mainsail sheeted in tight to avoid getting to close to the other boat, who was sailing parallel to the shore, and had deeper draft that we did.

Question: did our right to round the mark pre-empt their right to be in a position to request room at the obstruction that was within 3 boat lengths?

My drawing based on the facts indicated and a drawing provided on SA.

The notion of mark-room 'expiring' while the entitled boat is still in the zone has been reintroduced in the 2017 rules, after having had a holiday since the 2009 rewrite introducing the 3 hull length zone.

We need to look carefully at the words in the new rules, and can't rely on our recollections of old cases, although these might prove helpful.

Green (G) was overlapped inside Blue (B) when the first of them reached that zone, so B was required to give G mark-room (rule ( b )), (as well as keeping clear as the windward boat (rule )).

The mark-room G was entitled to was room to leave the mark on the required side. Also, (a) room to sail to the mark when her proper course is to sail close to it, and (B) room to round the mark as necessary to sail the course. (Definitions: ).

Once G had been given that mark-room, her entitlement to mark-room in accordance with rule ( b ) and (c) ceased to apply (rule ( d )). That is to say, once G had left the mark on the required side and it was no longer necessary for her to continue rounding it to sail the course, her entitlement to mark-room under under rules ( b ) and ( c ) ceased. In other words, her entitlement (under rules ( b ), and ( c )) to mark-room, ceased when she no longer needed it. The entitlement may cease before the mark becomes clear astern.

Note that even though an entitlement to mark-room under rule ( b ) and ( c ) may have ceased it may still be possible for a fresh entitlement to mark room for an inside overlapped boat to arise under rule ( a ).

In the diagram, G will have rounded the mark as necessary to sail the course when her heading clears, by a minimum prudent margin, the SW corner of the obstruction, that is, somewhere between position [5] and position [6]. That's the time when G's entitlement to mark-room ceases.

G's entitlement to mark-room certainly did not cease when she gybed around position [4]: mark-room includes room to gybe as necessary, and applies before and after the gybe if necessary.

G's entitlement to mark-room is not affected by any entitlement that B may have gained to room to pass the obstruction under rule . Rules and operate independently of one another. Neither rule takes precedence over the other.

It might be possible that the gap between the mark and the obstruction was so narrow that there was insufficient space for B to give G mark-room and for G to give B room to pass the obstruction, then B would break rule  and G would break rule . That would be very bad race management and hopefully a protest committee would, on valid request, give both boats redress.

Once G gybed, B became the right of way boat, even though she owed G mark-room. B is not required to anticipate that G will not keep clear and will not give G room at the obstruction (Case ). Nobodies obligations or entitlements are affected by whether they placed themselves in a position where they could, or could not later do something.