A stent graft assembly comprising: a. a first prosthesis comprising: i. a main body formed of biocompatible graft material having a proximal end and a distal end and a main lumen extending therebetween wherein the main lumen comprises a single lumen extending the length of the main body; ii. a bifurcated portion extending distally from the main body, the bifurcated portion comprising a first tubular portion defining a first lumen and a second tubular portion defining a second lumen, wherein the first and second lumens are in communication with the main lumen; and iii. wherein the main body portion tapers inwardly from the bifurcated portion to the proximal-most end of the main body, said proximal-most end being the most narrow end of the main body; b. a second prosthesis comprising: i. a tubular body of biocompatible graft material having a flared distal end portion; and c. a third prosthesis being a bifurcated prosthesis comprising first and second legs; d. wherein the flared distal end portion of the second prosthesis is configured to sealingly engage with the tapered main body of the first prosthesis e. wherein the second prosthesis is configured to be deployed to connect the first leg of the third prosthesis to the proximal end of the first prosthesis. a. a first prosthesis comprising: i. a main body formed of biocompatible graft material having a proximal end and a distal end and a main lumen extending therebetween wherein the main lumen comprises a single lumen extending the length of the main body; ii. a bifurcated portion extending distally from the main body, the bifurcated portion comprising a first tubular portion defining a first lumen and a second tubular portion defining a second lumen, wherein the first and second lumens are in communication with the main lumen; and iii. wherein the main body portion tapers inwardly from the bifurcated portion to the proximal-most end of the main body, said proximal-most end being the most narrow end of the main body; i. a main body formed of biocompatible graft material having a proximal end and a distal end and a main lumen extending therebetween wherein the main lumen comprises a single lumen extending the length of the main body; ii. a bifurcated portion extending distally from the main body, the bifurcated portion comprising a first tubular portion defining a first lumen and a second tubular portion defining a second lumen, wherein the first and second lumens are in communication with the main lumen; and iii. wherein the main body portion tapers inwardly from the bifurcated portion to the proximal-most end of the main body, said proximal-most end being the most narrow end of the main body; b. a second prosthesis comprising: i. a tubular body of biocompatible graft material having a flared distal end portion; and i. a tubular body of biocompatible graft material having a flared distal end portion; and c. a third prosthesis being a bifurcated prosthesis comprising first and second legs; d. wherein the flared distal end portion of the second prosthesis is configured to sealingly engage with the tapered main body of the first prosthesis e. wherein the second prosthesis is configured to be deployed to connect the first leg of the third prosthesis to the proximal end of the first prosthesis.