A compound of formula: wherein L is a linker with a backbone comprising at least one group, the or each group being independently selected from the list consisting of an optionally substituted C 1 -C 30 alkylene, an optionally substituted C 2 -C 30 alkenylene, an optionally substituted C 2 -C 30 alkynylene, NRs, O, S, SO, SO 2, an optionally substituted C 6 -C 12 arylene and an optionally substituted 5 to 10 membered heteroarylene, wherein the backbone of the linker is between 7 and 50 atoms in length; R 1 is an E3 ligand for an E3 ligase, which is: each R 2 is independently a halogen, OR3, NR 3 R 4, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, a C 6 -C 12 aryl group or a 5 to 10 membered heteroaryl group; R3 and R4 are independently H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl; p is 0 or an integer between 1 and 4; X 1 to X 7 and X 13 are each NH or O and R 7 is H, an optionally substituted C 1 -C 6 alkyl, an optionally substituted C 2 -C 6 alkenyl, an optionally substituted C 2 -C 6 alkynyl, an optionally substituted C 3 -C 6 cycloalkyl, an optionally substituted 3 to 6 membered heterocycle, an optionally substituted phenyl or an optionally substituted 5 or 6 membered heteroaryl; wherein the or each optionally substituted alkylene, optionally substituted alkenylene, optionally substituted alkynylene, optionally substituted heteroaryl and optionally substituted heteroarylene may be unsubstituted or substituted with one or more of halogen, oxo, OH, NH 2, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, a C 3 -C 6 cycloalkyl, a 3 to 10 membered heterocycle, a C 6 -C 12 aryl and/or a 5 to 10 membered heterocycle; and the or each optionally substituted arylene may be unsubstituted or substituted with one or more of halogen, OH, NH 2, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, a C 3 -C 6 cycloalkyl, a 3 to 10 membered heterocycle, a C 6 -C 12 aryl and/or a 5 to 10 membered heterocycle; or a pharmaceutically acceptable salt, solvate or tautomeric form thereof. R 1 is an E3 ligand for an E3 ligase, which is: each R 2 is independently a halogen, OR3, NR 3 R 4, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, a C 6 -C 12 aryl group or a 5 to 10 membered heteroaryl group; R3 and R4 are independently H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl or C 2 -C 6 alkynyl; p is 0 or an integer between 1 and 4; X 1 to X 7 and X 13 are each NH or O and R 7 is H, an optionally substituted C 1 -C 6 alkyl, an optionally substituted C 2 -C 6 alkenyl, an optionally substituted C 2 -C 6 alkynyl, an optionally substituted C 3 -C 6 cycloalkyl, an optionally substituted 3 to 6 membered heterocycle, an optionally substituted phenyl or an optionally substituted 5 or 6 membered heteroaryl; wherein the or each optionally substituted alkylene, optionally substituted alkenylene, optionally substituted alkynylene, optionally substituted heteroaryl and optionally substituted heteroarylene may be unsubstituted or substituted with one or more of halogen, oxo, OH, NH 2, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, a C 3 -C 6 cycloalkyl, a 3 to 10 membered heterocycle, a C 6 -C 12 aryl and/or a 5 to 10 membered heterocycle; and the or each optionally substituted arylene may be unsubstituted or substituted with one or more of halogen, OH, NH 2, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, a C 3 -C 6 cycloalkyl, a 3 to 10 membered heterocycle, a C 6 -C 12 aryl and/or a 5 to 10 membered heterocycle; or a pharmaceutically acceptable salt, solvate or tautomeric form thereof.