@Clubman - you dont seem to grasp the fundamentals of how loan interest is calculated. This isn't a problem per se, except that you reply to other posters here with an air of authority and people would be lead to believe that you are giving them correct information.
If you believe that you are borrowing the €1,300 for a full 52 weeks then fine but, in reality you are not. Your principal outstanding is dropping every week. Look at the table below which shows you teh amortised cashflow of payments split between capital and interest over the 52 weeks (can you work out the interest charged in the 1st week? then do the same for each week by reference to the principal remaining at the start of that week! ):
Principal Pay Int Principal
1,300.00 (26.23) (2.38) (23.86)
1,276.15 (26.23) (2.33) (23.90)
1,252.25 (26.23) (2.29) (23.94)
1,228.30 (26.23) (2.24) (23.99)
1,204.32 (26.23) (2.20) (24.03)
1,180.29 (26.23) (2.16) (24.07)
1,156.21 (26.23) (2.11) (24.12)
1,132.10 (26.23) (2.07) (24.16)
1,107.94 (26.23) (2.02) (24.21)
1,083.73 (26.23) (1.98) (24.25)
1,059.48 (26.23) (1.94) (24.29)
1,035.18 (26.23) (1.89) (24.34)
1,010.85 (26.23) (1.85) (24.38)
986.46 (26.23) (1.80) (24.43)
962.04 (26.23) (1.76) (24.47)
937.56 (26.23) (1.71) (24.52)
913.05 (26.23) (1.67) (24.56)
888.48 (26.23) (1.62) (24.61)
863.88 (26.23) (1.58) (24.65)
839.23 (26.23) (1.53) (24.70)
814.53 (26.23) (1.49) (24.74)
789.79 (26.23) (1.44) (24.79)
765.00 (26.23) (1.40) (24.83)
740.17 (26.23) (1.35) (24.88)
715.29 (26.23) (1.31) (24.92)
690.37 (26.23) (1.26) (24.97)
665.40 (26.23) (1.22) (25.01)
640.38 (26.23) (1.17) (25.06)
615.32 (26.23) (1.12) (25.11)
590.22 (26.23) (1.08) (25.15)
565.06 (26.23) (1.03) (25.20)
539.87 (26.23) (0.99) (25.24)
514.62 (26.23) (0.94) (25.29)
489.33 (26.23) (0.89) (25.34)
464.00 (26.23) (0.85) (25.38)
438.62 (26.23) (0.80) (25.43)
413.19 (26.23) (0.75) (25.48)
387.71 (26.23) (0.71) (25.52)
362.19 (26.23) (0.66) (25.57)
336.62 (26.23) (0.62) (25.62)
311.01 (26.23) (0.57) (25.66)
285.34 (26.23) (0.52) (25.71)
259.64 (26.23) (0.47) (25.76)
233.88 (26.23) (0.43) (25.80)
208.08 (26.23) (0.38) (25.85)
182.23 (26.23) (0.33) (25.90)
156.33 (26.23) (0.29) (25.94)
130.39 (26.23) (0.24) (25.99)
104.39 (26.23) (0.19) (26.04)
78.36 (26.23) (0.14) (26.09)
52.27 (26.23) (0.10) (26.13)
26.13 (26.18) (0.05) (26.13)