Swansea West MP Alan Williams has taken up a special senior role as Father of the House in the new Parliament which convened on Wednesday.
Alan Williams MP was first elected in 1964
Labour's Mr Williams, 74, inherited the title when he became the MP with the longest unbroken service last week.
The previous holder, Tam Dalyell, stepped down at the general election.
Mr Williams, who was first elected in 1964, presided over the unopposed re-election of Michael Martin as Speaker of the House of Commons.
Mr Williams, who currently chairs the Liaison Committee, said becoming Father of the House was "an honour".
"It is one you gain by attrition - if survivability is a merit, it has been rewarded," he said.
Mr Williams, a former industry minister and shadow Welsh Secretary, said he had been given coaching in his lines for the ceremony to elect the Speaker.
"For a brief spell, I hold all the disciplinary powers of the House of Commons - for about four minutes flat," he said.
"It is really pressing the start button for the new Parliament."
The role of Father of the House does not carry many duties, but could also see him fielding questions from MPs from all parties.
"Each party now organises their own inductions, but I will be available for any questions, from the whole house," he said.
He said that, in the build-up to the election, Mr Dalyell had approached him to say he was standing down.
But Mr Williams said that the prospect of becoming Father of the House had not influenced his decision of whether or not to stand.
"I just enjoy what I am doing the House of Commons," he said.
Tam Dalyell stood down after 43 years in Parliament
"It sounds twee but every day I walk into the House of Commons, I get a kick out of it and I hope all new MPs feel the same."
But he did say he would not be standing again.
"I made it clear this would be my last electoral battle," he said.
However, after more than 40 years in Parliament, nothing has matched his first impressions of life as an MP.
"[My highlight is] the first day I was elected in Swansea West - it was such a wonderful feeling," he said.
Although he is Father of the House, he is not the oldest MP, or the one elected earliest.
Ealing Southall MP Piara Khabra, who represents Labour, is 81, while 75-year-old Conservative Sir Peter Tapsell was first elected in 1959, but lost his seat in 1964.
Previous Welsh politicians to have held the post include Sir James Callaghan and David Lloyd George.