A subsea hydrocarbon production system which comprises: a tubing hanger (16; 704) which is positioned at an upper end of a well bore, the tubing hanger (16; 704) including a tubing hanger production bore (20; 708); a tubing string which extends from the tubing hanger (16; 704) into the well bore and is fluidly connected to the tubing hanger production bore (20; 708); a christmas tree (10; 100; 200; 300; 400; 500; 700; 1000) which is positioned above the tubing hanger (16; 704; 808) and which comprises: a production bore (28; 710) which is fluidly connected to the tubing hanger production bore (20; 708); a production outlet (32; 712) which is connected to the production bore (28; 710); a first barrier element (54; 112; 114) which is positioned in the production outlet (32; 712); and a first closure device (64; 110; 110a; 110b; 111; 502; 606; 608; 622; 714) which is positioned in the production bore (28; 710) above or below the production outlet (32; 712); wherein access from above the christmas tree (10; 100; 200; 300; 400; 500; 700; 1000) through the production bore (28; 710) does not require passage through a barrier element (54; 112; 114; 816); characterized in that the system further comprises: a downhole equipment device which is positioned in the tubing string, the downhole equipment device being connected to a suspension string (602; 722) which is connected to a downhole equipment hanger (604; 604a; 716; 730) that is secured to the tubing hanger production bore (20; 708); wherein the downhole equipment hanger (604; 604a; 716; 730) is located below the first closure device (64; 110; 110a; 110b; 111; 502; 606; 608; 622; 714). a tubing hanger (16; 704) which is positioned at an upper end of a well bore, the tubing hanger (16; 704) including a tubing hanger production bore (20; 708); a tubing string which extends from the tubing hanger (16; 704) into the well bore and is fluidly connected to the tubing hanger production bore (20; 708); a christmas tree (10; 100; 200; 300; 400; 500; 700; 1000) which is positioned above the tubing hanger (16; 704; 808) and which comprises: a production bore (28; 710) which is fluidly connected to the tubing hanger production bore (20; 708); a production outlet (32; 712) which is connected to the production bore (28; 710); a first barrier element (54; 112; 114) which is positioned in the production outlet (32; 712); and a first closure device (64; 110; 110a; 110b; 111; 502; 606; 608; 622; 714) which is positioned in the production bore (28; 710) above or below the production outlet (32; 712); a production bore (28; 710) which is fluidly connected to the tubing hanger production bore (20; 708); a production outlet (32; 712) which is connected to the production bore (28; 710); a first barrier element (54; 112; 114) which is positioned in the production outlet (32; 712); and a first closure device (64; 110; 110a; 110b; 111; 502; 606; 608; 622; 714) which is positioned in the production bore (28; 710) above or below the production outlet (32; 712); wherein access from above the christmas tree (10; 100; 200; 300; 400; 500; 700; 1000) through the production bore (28; 710) does not require passage through a barrier element (54; 112; 114; 816); a downhole equipment device which is positioned in the tubing string, the downhole equipment device being connected to a suspension string (602; 722) which is connected to a downhole equipment hanger (604; 604a; 716; 730) that is secured to the tubing hanger production bore (20; 708); wherein the downhole equipment hanger (604; 604a; 716; 730) is located below the first closure device (64; 110; 110a; 110b; 111; 502; 606; 608; 622; 714).