@GoAt Yes, you are correct. HMRC rules stipulate that only cash^ may go into an ISA (that is the way the HMRC monitors the £20K limit). Hence shares owned outside an ISA need to be sold** and bought again inside an ISA (This sell and buy is termed as a “Share exchange” or a “Bed and ISA”).
^ Not strictly true - a direct transfer is allowed where the shares were issued to the investor under a schedule 3 SAYE option scheme or some other schemes that are related to employee perks.
**And naturally the sale of the original investment is a disposal for capital gains purposes.