Woman who 'had affair with Robert Rosenkranz' confronts wife on Twitter

• Katherine Nelson claims she had an affair with investor Robert Rosenkranz
• Nelson sent Rosenkranz's wife a tweet that said 'you must have known'
• It's alleged in a lawsuit that Rosenkranz once introduced Nelson as his wife
• The suit claims Rosenkranz tried to buy Nelson's silence over the affair
• It says that the New York investor offered to pay her $100,000 to keep quiet

By Ted Thornhill for MailOnline and Sara Malm for MailOnline

Published: 03:54 EST, 24 November 2014 | Updated: 12:09 EST, 24 November 2014

The self-proclaimed lover of a New York investment tycoon sent his wife an incendiary tweet of a note he allegedly wrote her, despite claiming to have signed a confidentiality agreement preventing her from discussing their four-year-long affair.

Katherine Nelson wrote ‘you must have known’ in the tweet to Alexandra Munroe, wife of multi-millionaire Delphi Financial Group CEO Robert Rosenkranz, 72.

It carried a picture of a note on cream-coloured stationary stamped with the businessman’s name that said ‘for me, two is a remarkable number’.

Taunt: The self-proclaimed lover of a New York investment tycoon sent his wife an incendiary tweet that included a picture of a romantic note he allegedly wrote her

Incendiary: Katherine Nelson (left) confronted Alexandra Munroe (right) on Twitter with a message that said 'you must have known'

Courting trouble: Ms Nelson claims in a lawsuit that she had a four-year-affair with Delphi Financial Group CEO Robert Rosenkranz, but that he tried to silence her with a money-for-sex gagging order

Munroe, the 57-year-old Senior Curator of Asian art at the Guggenheim museum replied with a blank tweet, the New York Post reported.

Ms Nelson has filed a lawsuit that claims she began an affair with Mr Rosenkranz, a Harvard and Yale graduate who is a member of the Council on Foreign Relations, four years ago and that he even once introduced her as his wife at a Yale University meeting, according to the New York Daily News.

The suit alleges that in May this year Mr Rosenkranz duped her into signing a ‘money-for-sex’ agreement that ordered her not to discuss the relationship sweetened by the promise of a six-figure sum, the paper said.

Bought off: Ms Nelson claims that the 72-year-old Delphi Financial Group CEO promised her $100,000 in exchange for a confidential sexual relationship

Multimillionaire financier Robert Rosenkranz's wife Alexandra Munroe, 57, is Senior Curator of Asian art at the Guggenheim museum

Hell hath no fury: Ms Nelson filed the lawsuit after seeing her alleged lover with another woman - not his wife - and broke down in the middle of the restaurant after he pretended not to know who she was

Ms Nelson says she signed the document without a lawyer present as Rosenkranz said it was ‘just between them’ and claims that he promised her $100,000, money that she claims never to have received.

According to court papers the pair ‘exchanged several hundred e-mails over a period of approximately four years with topics ranging from a private sexual nature to politics, literature and finance’ and exchanged ‘romantic presents from Tiffany, Hermes and Paul Stuart’.

They would rendezvous at Mr Rosenkranz’s Manhattan office and in Aspen, the papers said.

The Aspen property where they are said to have been meeting up, was listed by its former owner for $22.5million, but the price paid by Mr Rosenkranz is not known.

The 7,800-square-foot property has five bedrooms and was featured in Elle Decor.

Romantic getaway: The picture shows the $22.5m Aspen house where Rosenkrantz would take Ms Nelson

The married multimillionaire would whisk Ms Nelson away to this Aspen property, she claims

As well as dates in Aspen and New York, Ms Nelson and Mr Rosenkranz ‘exchanged several hundred e-mails over a period of approximately four years'

Steamy affair: Ms Nelson claims she and the 72-year-old multimillionaire exchanged ‘romantic presents from Tiffany, Hermes and Paul Stuart’.

The relationship between the 72-year-old multimillionaire and his 31 years younger mistress came to an end when Ms Nelson spotted him with another woman at BLT Steakhouse, he pretended not to know her.

She broke down crying and was asked to leave by restaurant staff.

The papers add that when Ms Nelson told him she was going to write a book, he reached for her throat.

Mr Nelson, a well-known philantropist, married arts curator Ms Munroe at the Presbyterian Church in Bridgehampton in 2002.

Their wedding announcement in the New York Times, notes that Mr Nelson's 'previous marriage ended in divorce'.

Mr Rosenkranz declined to comment when contacted by MailOnline.