Lord Sainsbury, who served as a minister in Tony Blair and Gordon Brown's governments, gave over £2m each to the Liberal Democrats and Labour in the second quarter of this year.
BBC News quotes a Lib Dem spokesman:
"We have enormous respect for Lord Sainsbury, and we see his help in the referendum campaign as a huge endorsement of this party's campaigning strength and our unequivocally pro-European ideals,"You bet we have respect for him.
David Sainsbury joined the Labour Party in the 1960s, but became a founder member and a member of the SDP in the 1980s.
He supported David Owen's Wee Frees when the SDP merged with the Liberal Party. When Owen's Continuing SDP gave up the ghost Sainsbury rejoined Labour and served as a minister the House of Lords under both Tony Blair and Gordon Brown.
He is just one man, but his support of the Lib Dems may calm fears that some sort of reorganisation in British politics will take place without us being invited.